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Prenatal testing is the best strategy for reducing the burden of genetic disorders and congenital disabilities that cause significant postnatal functional impairment. Universal prenatal screening is advisable for common genetic disorders and congenital anomalies such as Down syndrome, beta-thalassaemia and neural tube defects. Several prenatal-screening tests are now available for Down syndrome, but knowledge about the appropriate timing of the test and the need for pre- and post-test counselling may not be updated among the primary care physicians. There is also a considerable degree of confusion regarding the prenatal screening test to be chosen in each case, due to the availability of a number of new and advanced screening techniques. At present, there is no nation-wide consensus regarding the nature and timing of these prenatal-screening protocols. Due to the absence of any definite guidelines and the additional lacunae in the awareness regarding the appropriate prenatal screening in the country, the optimum benefits of these screening protocols are not reaching the population. This review focuses on the various prenatal screening and diagnostic tests that are available for common genetic conditions and congenital disabilities and attempts to outline the most cost-effective and gestational age-appropriate strategies for prenatal screening for the Indian healthcare set-up. The recommendations suggested would serve as a source guide for formulating prenatal-screening guidelines for reducing the incidence of common genetic disorders and congenital disabilities in India., Competing Interests: None

Background: The objectives of this study were to explore the prevalence of neural tube defects (NTDs) in three districts of Beijing, and to evaluate the impact of prenatal diagnosis on the prevalence., Methods: Data were collected between 2006 and 2012 from the Beijing Birth Defects Surveillance System. P 13 and P 28 represent the prevalence of NTDs diagnosed from 13 weeks and 28 weeks of gestation, respectively, to 7 days after delivery. Populations were classified as household (permanent) and non-household (non-permanent) because differences exist in access to health care, education, and income, among others., Results: The P 13 of NTDs was 11.7 per 10 000 births in the three districts, which declined from 2006-12. In addition, the prevalence of NTDs in the non-household population was 1.7-fold higher than that among the household population. The P 13 of anencephaly, spina bifida, and encephalocele were 5.3, 4.9, 1.6, respectively, per 10 000 births. The P 28 of NTDs only represented 29.1% of P 13 , and this proportion decreased over the 7-year period., Conclusions: The prevalence of NTDs remains high in the three districts of Beijing, and the rate was higher in the non-household than household population. The prevalence of birth defects would be under estimated by almost 70 per cent if the report time was set on 28 weeks' gestation or later compared with report time on 13 weeks of gestation. It is better to set the report time earlier in birth defect surveillance in contemporary China., (© 2017 John Wiley & Sons Ltd.)

Objectives: The aim of the study was to analyze the origin of birth defects in pregnant women from the Kujawy-Pomerania Region, and to identify factors affecting the formation of developmental disorders in the Province., Material and Methods: The correlation between maternal age and fetal defects was investigated. We also attempted to determine whether environmental or family factors play a role in the formation of fetal abnormalities., Results: The analysis confirmed a correlation between the incidence of chromosomal aberrations and maternal age., Conclusions: Higher rates of neural tube defects were observed in fetuses born to mothers who did not take folic acid. The influence of other factors on developmental anomalies was not confirmed.

Background and Objective: The study of congenital defects (CD) must include termination of pregnancy (TOP) for CD and evaluate risk factors that modify their frequency., Patients and Methods: Consecutive series of 517 newborn and 202 TOP with CD among 38,191 childbirths, between 1982-2009 years., Results: The mean frequency for newborns with CD is 13.54‰ and for newborn and TOP with CD is 18.73‰. Single CD are 61.12% in newborns and 52.17% in TOP. The 18.37% of CD in newborn and 40.58% of TOP are syndromic. Mean gestational age for TOP is 17.92 weeks. Overall frequency of anencephaly is 2.62‰ for newborns and 6.77 for 10,000 for newborns and TOP. Spina bifida is 3.14 for 10,000 newborns and 5.99 for 10,000 newborns and TOP. Overall frequency of Down syndrome (DS) is 10.74 for 10,000 newborns and 22.14 for 10,000 newborns and TOP. The percentage of foreign mothers was 35.9% in 2009 and the mean maternal age significantly increased in this period., Conclusion: We observe a significant decrease of CD in newborns but not in their conception. We have not detected primary prevention for neural tube defects. The decrease in DS in newborns is not statistically relevant but ethnic diversity and maternal aging may be modifying the frequency. The 53% of CD were TOP in the period 2007-2009. It is mandatory a complete study for CD in TOP in order to offer serious reproductive counselling., (Copyright © 2012 Elsevier España, S.L. All rights reserved.)

The aim of this study was to analyze the sociodemographic features, postoperative complications, long-term problems, and cost of care of patients followed in the neonatal intensive care unit (NICU) with a diagnosis of neural tube defects (NTDs). Babies with NTD followed in the Neonatology Unit of Ondokuz Mayıs University Faculty of Medicine between January 2003 and December 2011 were analyzed retrospectively. One hundred (1.2%) of 8408 babies admitted to the NICU were diagnosed as NTD during the study period. Of the cases with NTD, 74% of mothers were graduates of primary school/illiterate, and none had used folic acid (FA) preconceptionally. Prenatal diagnosis was made in 72%, but parents had chosen not to terminate the pregnancy. The most frequent type and site of NTD was meningomyelocele (82%) of the lumbosacral region (36%). In 80% of the babies, the NTD sac was closed with in the first 72 hours of life. The most frequently observed postoperative complications were wound infection and septicemia. The mortality rate of babies with NTD during the follow-up period was 7%, and all deaths occurred in the first year of life. Sixty-two percent of the patients had neurologic deficits on follow-up. Patients were rehospitalized during the follow-up for an average of 2.9 times. Neural tube defect (NTD) is a disabling problem, with operations, rehospitalizations and other costly treatments. Maternal education regarding preconceptional FA use/fortification of food with FA and appropriate guidance to the family with prenatal diagnosis will decrease the incidence and burden of the disease.

Objective: Down syndrome (DS) has major resource implications especially in developing countries being third most important cause of mental handicap. Maternal serum screening for chromosomal aneuploidies and neural tube defects (NTDs) is practiced worldwide in many countries and has been integrated into mainstream health care, while it is gradually gaining momentum in Asian countries., Methods: This prospective cohort study was carried out in pregnant women undergoing triple screening test between January 2007 and December 2010 after informed consent. Biomarkers alpha-fetoprotein, human-chorionic-gonadotropin and unconjugated-estriol were tested, and risk of pregnancy being affected with DS, Edward's syndrome or NTDs were calculated. Screen-positive patients were referred for detailed ultrasonography and confirmatory amniocentesis. Follow-up record was maintained until delivery., Results: Of 7400 pregnant women enrolled, 419(5.7%) were screen-positive, including 339 positive for DS, two for trisomy 18, and 62 for NTDs. Total eight cases of DS were eventually diagnosed in the population (prevalence of DS = 1 : 925), seven of which were detected in utero following diagnostic evaluation for positive serum screen (DR of DS screen = 87.5%). Total five cases of NTD were observed, yielding NTD prevalence of 0.67/1000., Conclusions: Triple screening in the second trimester is reasonably effective for the detection of major chromosomal defects and NTDs, and can be implemented successfully also in India., (© 2012 John Wiley & Sons, Ltd.)

Objective: To investigate key techniques and intervention in reducing birth defects., Method: Down's syndrome (DS), trisomy-18 (Edwards syndrome, ES), neural tube defects (NTD), Duchenne muscular dystrophy (DMD), spinal muscular atrophy (SMA), thalassemia, and glucose-6-phosphate dehydrogenase deficiency (G6PD) were chosen as target disease. From Jan. 2007 to Dec. 2009, the condition of intake folic acid were investigated in 5004 pregnant women in Panlong District and Wuhua District of Kunming City. All of the 27 660 pregnant women undergoing prenatal examination were enrolled into the study from the First People's Hospital of Yunnan Province, the Second People's Hospital of Yunnan Province, the First People's Hospital of Qujing City, the Second People's of Qujing City, Qujing Women and Children's Hospital, People's Hospital of Lincang City, Kunming Maria Women's Hospital, Maternal and Infant's Care Unit of Panlong District of Kunming City, Maternal and Infant's Hospital of Dali City. The screening was performed on serum of those pregnant women at 8 - 20(+6) gestational weeks. Prenatal cytogenetic analysis and fetal ultrasonograpy were performed on the high risk or indicated women after genetic counseling. DNA analysis was administered on those women with family or childbearing history of DMD, SMA, thalassemia, or G6PD. Outcome of pregnancy was followed up to evaluate the effect of intervention., Results: Approximately 30.10% (1506/5004) of pregnant women were administered by oral folic acid during perinatal period. Two thousand three hundred and thirteen women with high risks of DS, ES, or NTD fetuses were observed among 27 660 undergoing maternal serum screening. Two thousand and ninety-six pregnant women including two twins pregnant women were performed cytogenetic analysis. Other 67 pregnant women at high risk of DMD, SMA, thalassemia, and G6PD accepted genetic counseling and prenatal gene analysis. Two thousand one hundred and sixty-three pregnant women (2165 fetuses) underwent prenatal examination. One hundred and two cases chromosome abnormalities, 17 cases NTD, 4 cases DMD, 1 cases α-thalassemia major were found. All of the 91 fetuses with major birth defects were terminated after genetic counseling. Another affected DS fetus in a twin pregnancy dead intrauterine at 24 gestational weeks. Thirty-two women bearing fetuses with balanced translocations or inversions continued their pregnancies. Totally 2071 normal term fetuses were born in the prenatal diagnosis group. Two fetuses with normal chromosome were lost within 1 week after amniocentesis. Four affected DS fetuses were born from their high risk mothers who refused further prenatal diagnosis service. In a random sampling follow-up cohort of 5000 mothers at low risk, none of affected child suffering target diseases was found. The DS detection rate of maternal serum screening was 84% (27/32), with the false positive rate was 6.153% (1702/27 660)., Conclusions: Folic acid intake before conception and in the first trimester would reduce the risk of birth defects, only 1/3 reproductive women took folic acid actively. Maternal serum screening could effectively detect high risk of DS, ES and NTD. The genetic counseling is critical in women at high risk or who had family history of inherited disorders. The prenatal screening and diagnosis combined with routine obstetric care could reduce the incidence of major birth defects, which should become prenatal care strategy in our country.

Objective: To describe the frequency and prevalence trend for neural tube defects (NTD) (anencephaly, spina bifida and encephalocele) in Asturias (Spain), as well as the impact of prenatal diagnosis programs., Methods: All cases of NTD in births and induced abortions were studied, using data from the Registry of Congenital Defects of Asturias for 1990-2004. Total and birth prevalence rates were calculated., Results: The prevalence of NTD for 1990-2004 was 12.2 per 10,000 births (5.9 anencephaly, 5.0 spina bifida and 1.3 encephalocele) and showed a slightly decreasing trend due to a significant decline in spina bifida prevalence. The prevalence of anencephaly and encephalocele remained stable. The percentage of induced abortions after prenatal diagnosis among all NTD was 88% (anencephaly 96.7%, spina bifida 80% and encephalocele 84.6%), leading to a very low birth prevalence (1.4 per 10,000) for the entire period., Conclusions: The total prevalence of spina bifida has decreased in the last 15 years in Asturias. Secondary prevention through prenatal diagnosis and interruption of affected pregnancies have resulted in a marked decrease in NTD at birth. The recommendation of periconceptional use of folic acid seems not to have achieved the desired effect.

Background: Neural tube defects (NTDs) are common and serious birth defects all over the world. Prenatal screening for NTDs using maternal serum alpha-fetoprotein (MSAFP) during the second trimester of pregnancy has been widely used, but its effectiveness remains unclear., Methods: We evaluated the studies published in the English and Chinese on MSAFP screening for NTDs. The homogeneity of the studies was evaluated by the forest graph. Meta-analysis was applied to calculate the combined effect values and their 95% confidence intervals., Results: As many as 22 articles were selected according to the criteria and were included in the meta-analysis, for a total of 684,140 pregnant women screened during the second trimester. All the studies selected were homogenous according to the forest graph (chi(2) = 25.17, P > 0.10). The combined relative risk estimate was 0.25 and its 95% confidence interval was 0.21 to 0.29. The combined protective rate was 75%. The sensitivity and specificity of MSAFP screening were 75.1 and 97.7%, respectively., Conclusion: Use of MSAFP during the second trimester in pregnant women is an effective measure for the screening of NTDs.

Objective: This study was conducted to evaluate the major demographic details, diagnostical and clinical features, as well as the risk of recurrence of cases with the major types of neural tube defects (NTD). We also examined the efficiency of ultrasonography based on autopsy examinations during 26 years., Methods: The investigations were made into the sample of 743 NTD diagnosed between 1 January 1976 and 31 December 2002. A computerized database was used to sum up the available information about the individual cases; in addition to surveying the couples' major demographic details, we also had the opportunity to collect detailed information about the history, diagnostics (ultrasound) and outcome of the pregnancies as well as the results of the autopsies during the investigation., Results: In the 743 cases of NTD, maternal and paternal median ages turned out to be 23.7 years (+/-5.22 years) and 28.7 years (+/-5.81 years), respectively. The male:female ratio was 0.78. Comparable samples of anencephaly and spina bifida allowed for the conclusion that a positive genetic history was equally often found while a positive obstetrical history was almost twice as common in anencephaly. The sensitivity of the maternal serum-alpha fetoprotein (AFP) screening test is the highest in anencephaly and lowest in encephalocele. While the majority of cases of anencephaly were diagnosed before the 24th gestational week, examples of diagnosing spina bifida and encephalocele at a later time could also be found. Among the associated malformations other than those of the central nervous system special mentioning should be made of fetal pyelectasia, cleft palate as well as diaphragmatic herniation. No pathological karyotypes were found in association with encephalocele or spina bifida, but anencephaly was accompanied with trisomy 21 and trisomy 18 in one case each. Anencephaly was found to have the highest risk of recurrence in both nervous system malformations and malformations other than those of the nervous system. Sonography proved to be the most reliable method in cases of enecephalocele., Conclusion: The respective median values of maternal and paternal age show that aetas has no role in the occurrence of NTDs. NTDs are more common among girls. Positive genetic, obstetrical and medical findings are of great importance in the incidence of NTDs. Although reliable to only a limited extent, maternal serum-AFP tests are considered to be useful and necessary in screening NTDs, while sonography is the gold standard method in recognizing these frequent malformations. The knowledge of the eventual associated malformations is mainly important in certain cases of spina bifida, which may also yield a good post-natal prognosis. Our data obtained from the sample of 26 years also confirm that the periconceptional administration of folic acid reduces the incidence and risk of recurrence of NTDs.

Objective: Determine the relationship between positive screening interpretations for Smith-Lemli-Opitz syndrome (SLOS) and other fetal abnormalities, to aid counseling and diagnostic activities., Methods: An SLOS screening algorithm was incorporated into California's second-trimester screening program for Down syndrome and open neural tube defects (ONTDs). Between 2002 and 2004, 777 088 pregnant women were given an SLOS risk interpretation, using alpha-fetoprotein (AFP), unconjugated estriol (uE3), and human chorionic gonadotrophin (hCG) measurements. Outcomes were obtained in 98.8% of screen-positive pregnancies., Results: SLOS screen positives, alone or in combination with screen positives for other fetal disorders (Down syndrome, trisomy 18, ONTD), were associated with a high risk for fetal pathology. Type and frequency of chromosomal or anatomic abnormalities (or fetal death) varied according to screen-positive combination. Among 2018 screen-positive pregnancies, 644 fetal deaths were identified. Among the 1374 viable pregnancies, 519 were screen positive for SLOS alone; two SLOS cases and 51 other serious abnormalities were identified (14 aneuploidies; 37 anatomic). The remaining 855 were also screen positive for at least one other disorder; two SLOS cases and 327 other abnormalities were identified (180 aneuploidies; 157 anatomic)., Conclusion: For screening programs implementing the SLOS algorithm, the present data may be useful for counseling and to guide diagnostic studies.

We studied 253 women with a pregnancy complicated by a birth defect and 506 controls to determine the frequency and type of prenatal tests and the types of defects detected antenatally. Most women had at least one ultrasound examination, but the frequency of other screening tests was low. Only 38 (15%) of defects were detected antenatally (37 by ultrasound). Birth prevalence is unlikely to be affected by pregnancy termination.

An audit was made of laboratory records of triple test results from 943 Palestinian women residing in the West Bank from 2000-03. The mean expected age at delivery of the subjects was 25.5 years; 12% were 35 years old or above. Age was the main factor associated with an abnormal calculated risk score. The frequency of elevated serum alpha-fetoprotein was 1.3%, abnormal human choriogonic gonadotropin (elevated or reduced) was 1.9% and reduced unconjugated estriol was 0.3%.

Objectives: To describe the maternal serum marker patterns of triploid pregnancies and estimate the second-trimester prevalence of triploidy., Methods: Forty-two cases of triploidy were identified in six serum screening programmes, five in the United Kingdom, one in Canada. This study describes the serum marker patterns, serum screening results for Down syndrome, trisomy 18 and open neural tube defects, and maternal age of these triploidy cases. The risk cut-off levels were > or = 1 in 250 for Down syndrome, > or =2.5 MoMs alpha-fetoprotein for open neural tube defects and > or =1:100 for trisomy 18 screening. The estimated second-trimester prevalence of triploidy was based on 22 triploidy cases ascertained in 599 934 pregnancies from three routine screening programmes, which attempted complete ascertainment of aneuploidy cases., Results: The observed second-trimester rate of triploidy was 0.37 per 10 000 fetuses. Two different serum marker patterns were seen in triploid pregnancies, distinguished from each other by typically very high or very low levels of total hCG or free beta-hCG. The median maternal ages were respectively 33 years for triploidy with human chorionic gonadotrophin levels < 1.0 MoM, and 26 years for those with hCG levels > or =1.0 MoM. Fifty-seven percent of the pregnancies with a triploid fetus had a risk estimate > or =1:100 for trisomy 18 alone, 10% had an alpha-fetoprotein > or =2.5 MoM, 5% were screen positive for Down syndrome alone, and 19% had an increased risk or positive results for more than one anomaly., Conclusion: The simultaneous use of maternal serum tests designed to screen prenatally for Down syndrome, neural tube defects, and an increased risk of trisomy 18 resulted in a screen-positive result for 90% of pregnancies with triploidy., (Copyright 2005 John Wiley & Sons, Ltd.)

Introduction: Neural tube defects (NTDs) can be considered as a folate deficiency disorder. The prevalence of NTDs ranges from about 0.5 to 6 in 1,000 births., Discussion: Two steps can be distinguished in biochemical screening for NTDs: 1. Screening in the general population, which is based on two complementary methods, maternal serum AFP screening and ultrasound screening; 2. Screening in a high-risk group, which requires fetal scanning by an expert sonographer., Conclusion: Amniocentesis for acetylcholinesterase electrophoresis is indicated when sonographic scans are difficult to interpret.

Achieving and maintaining the proper balance between detecting fetuses with open spina bifida or Down syndrome while maintaining an acceptably low screen-positive rate requires careful, ongoing monitoring of screening performance indicators along with specific procedures aimed at taking rapid and effective corrective actions when warranted. The process of epidemiologic monitoring, which uses data generated from the screened population, has been developed as an extended quality assurance measure for this purpose. The primary indicators used include the percentage of women with a screen-positive result and the grand multiple of the median. These indicators are sensitive to inaccurate and imprecise assay values and help to ensure that gestational age-specific median values are appropriate. Epidemiologic monitoring also provides useful information for physicians, public health authorities, and regulatory bodies.

Maternal serum screening has gained widespread acceptance as a major prenatal screening tool for chromosomal abnormalities in the US and Europe since Merkatz et al described an association between low maternal serum alpha fetoprotein (AFP) levels and increased risk for trisomy 21 in 1984. In 1988, Wald et al proposed a screening program based on maternal age in combination with three biochemical markers--AFP, hCG and unconjugated estriol. This study from January 1996--September 2002 included 1,793 pregnant women (between 14-22 weeks gestation) which were divided into 2 groups--1,083 women > 35 years (60.40%) and 710 women < 35 years (39.60%). A second trimester risk for trisomy 21 > 1 : 270 was considered a positive screen and genetic counseling to discuss risks and benefits of amniocentesis was offered. This study had 1,376 cases (76.7%) with negative screening (not increased risk for DS and NTD), 21 (1.2%) with negative screening (not increased risk for DS only) ; 292 (16.3%) with increased risk for DS; 5 cases (0.3%) with increased risk for DS and elevated AFP; 19 cases (1.1%) with elevated AFP; 33 cases (1.8%) with previous DS only; and 9 cases (0.5%) with previous NTD only. Two percent (2.1%) of the results could not be interpreted either because the test was done too early, too late or were grand multiple pregnancies. This study demonstrated that multiple marker screening offers another option for older women who traditionally have all been considered candidates for amniocentesis.

We set out to present the incidences of the neural tube defects (anencephaly, spina bifida and encephalocele) and to document maternal age distribution and the influence of the prenatal diagnostics on incidences in neonates. We also analysed maternal age as a risk factor for the defects studied. This was a retrospective epidemiological study of neural tube defects using data from the population-based register of congenital malformations in the Czech Republic over the 1961-99 period. The total number of neural tube defects detected both pre- and postnatally was 4696 in this period (anencephaly 1857, spina bifida 2420 and encephalocele 419 cases). In this period, a significant decrease (due to improved prenatal diagnostic efficiency) in the above-mentioned defects occurred in the Czech Republic. No statistically significant correlation between any of the particular defects and the maternal age was revealed. However, neural tube defects as a whole show some correlation, the probability of these defects occurring being higher than expected in 15- and 32-year-old mothers. By application of the two-sided 95% CI, statistically significant correlation was found in 15-, 35- and 39-year cohorts; in other age-groups above the age of 32 years this correlation was neither confirmed nor rejected. In this study, maternal age as a risk factor for the origin of neural tube defects has not been statistically confirmed. However, probability estimate makes this correlation possible. Statistical methods in use reveal the risk for these defects (regarding their relative incidences) only in maternal age groups of 15, 35 and 39 years.

Background: Prenatal screening and the promotion of folic acid intake could affect the incidence of neural tube defects (NTDs). We examined trends in the total NTD incidence, as detected in live births, stillbirths and therapeutic abortions, from 1986 to 1999 in Ontario., Methods: To capture cases of NTDs we used data from the Canadian Congenital Anomalies Surveillance System and hospital data on therapeutic abortions. We calculated the total incidence of NTDs by combining the numbers of NTDs occurring in live births, stillbirths and therapeutic abortions., Results: The total NTD incidence rate increased from 11.7 per 10,000 pregnancies in 1986 to 16.2 per 10,000 in 1995, and it subsequently decreased to 8.6 per 10,000 by 1999. The NTD birth rate (live births and stillbirths) decreased from 10.6 per 10,000 births in 1986 to 5.3 per 10,000 in 1999. The rate of therapeutic abortions with an NTD or hydrocephalus rose from 17.5 per 10,000 abortions in 1986 to 50.7 per 10,000 in 1995 and fell to 28.7 per 10,000 abortions in 1999., Interpretation: The total NTD incidence rate increased from 1986 to 1995, probably because of increased prenatal screening and better detection of NTDs. The decline from 1995 to 1999 may have been due to increased folic acid intake among women at the time of conception.

The objectives of this study were to describe the impact of prenatal diagnosis on the birth prevalence of congenital anomalies over 21 years (1979-1999) in a well defined population in northeastern France (13,500 births per year). The material for this study came from the analysis of data from multiple sources on births and terminations of pregnancy after prenatal diagnosis of congenital anomalies in 279,642 consecutive pregnancies of known outcome. The study period was divided into three subgroups 1979-1988, 1989-1993 and 1994-1999. Between 1979-1988, 1989-1993 and 1994-1999, prenatal detection of congenital anomalies increased, respectively, from 12.0% to 25.5% and to 31.7%. Termination of pregnancy (TOP) increased in the same proportions during the three time periods. However, the increase of TOP was much higher for chromosomal anomalies than for nonchromosomal congenital anomalies. The birth prevalence of Down's syndrome fell by 80% from 1979-1988 to 1994-1999. Sensitivity of prenatal detection of congenital anomalies and TOPs were lower for isolated cases (only one malformation present in the fetus) than for multiple malformations in the same fetus. Sensitivity varied with the type of malformations: it was high for neural tube defect (79.7%) and urinary anomalies (50.7%) and low for congenital heart defects (16.4%). In conclusion, the introduction of routine prenatal diagnosis has resulted in a significant fall in the birth prevalence of children with congenital anomalies. However, this fall varied with the types of congenital anomalies.

Objective: To determine the influence of various factors on the prenatal diagnosis and elective termination of neural tube defects (NTDs) in Hawaii in 1986-1997., Methods: Data from a birth defects registry were analyzed and included 245 cases., Results: 74% of the cases were prenatally diagnosed and 48% were terminated. Anencephaly was more likely to be prenatally diagnosed and electively terminated than spina bifida or encephalocele. Other factors such as maternal age, race/ethnicity, place of residence, and elevated maternal serum alpha-fetoprotein influenced the prenatal diagnosis and/or elective termination of NTD-affected pregnancies. However, a given factor may influence prenatal diagnosis and elective termination in different ways., Conclusions: Various diagnostic and demographic factors can influence the prenatal diagnosis and the subsequent termination of NTD-affected pregnancies., (Copyright 2000 S. Karger AG, Basel.)

Objective: Evaluation of prenatal diagnosis of neural tube defects by ultrasound examination in unselected populations across Europe., Setting: Prenatal ultrasound units in areas that report to contributing congenital malformation registers., Methods: All cases with a suspected or confirmed neural tube defect and delivered within the 30 month study period were identified from 18 Congenital Malformation Registers from 11 European countries. Data on the pregnancy, prenatal scans, outcome of pregnancy, and information on different screening policies for each country were analysed., Results: 670766 deliveries occurred in the area covered by the registers during the study period. A neural tube defect was diagnosed at delivery in 542 cases. In 84% of these, the lesion was isolated (166 anencephaly, 252 spina bifida, 35 encephalocele). Of the 166 isolated cases with anencephaly, 96% were correctly identified prenatally; one was missed on scan, two were wrongly diagnosed, and four were not scanned (sensitivity 98%). 84% of the prenatal diagnoses were made before 24 weeks' gestation; 86% of isolated anencephalic pregnancies were terminated. Of the 252 cases of isolated spina bifida, 171 (68%) were correctly identified prenatally; 66% of these before 24 weeks' gestation. The diagnosis was missed on scan in 60 cases and 21 were not scanned (sensitivity 75%). The mean reduction in birth prevalence because of termination of pregnancy for spina bifida was 49% (range 6-100%). There was a wide variation between centres in prenatal detection rate (33-100%), termination of pregnancy of prenatally diagnosed cases (17-100%), and gestation both at diagnosis and termination of pregnancy., Conclusion: A high prenatal detection rate for anencephaly was reported by all registers. There is a large variation in prenatal detection and termination rates for spina bifida between centres, reflecting differences both in policy and culture.

Objective: To describe the epidemiological impact of prenatal diagnosis and selective abortion on the frequency of neural tube defects (NTD) in the period 1980-1992 in the Northern Netherlands in comparison with data from other European regions., Design: Descriptive., Setting: 17 'European registration of congenital anomalies' (EUROCAT) registrations, localized in 10 European countries., Method: Data were collected actively and retrospectively from multiple sources fed by voluntary registration of congenital anomalies in live births, stillbirths and pregnancies terminated because of congenital anomalies., Results: In Europe the total birth prevalence of NTD in the period 1980-1992 ranged from 5.3 per 10,000 in Switzerland to 29.0 per 10,000 in Glasgow, a difference of a factor 5.5. In live births the difference was ninefold: ranging from 2.0 per 10,000 in Paris to 18.8 per 10,000 in Dublin. The Netherlands had a conspicuously high prevalence among live births, higher than in other regions in continental Europe. For spina bifida the live birth prevalence both in other continental regions and in Glasgow was also lower than in the Netherlands. In Glasgow serum alpha-foetoprotein screening apparently led to frequent early prenatal diagnosis of NTD and to frequent termination of pregnancy. In Paris the use of ultrasound screening appears to lead to frequent later prenatal diagnosis, as well as frequent termination of pregnancy., Conclusion: In the Netherlands the impact of prenatal diagnosis and selective abortion is limited, so that primary prevention (periconceptional use of folic acid) is more important than in some other European countries.

In the 2 years between 1993 and 1995, we assayed alpha-fetoprotein (AFP) in 48,412 amniotic fluids (AFs). One thousand and eighty-six (2.2 per cent) measured > or = 2.0 MOM and these were subdivided into three groups; mildly (2.0-4.9 MOM), moderately (5.0-9.9 MOM), and very elevated (> or = 10.0 MOM). Abnormalities occurred in 25 per cent of the mildly elevated compared with 88 per cent of the moderately and 98 per cent of the very elevated cases. Forty-five per cent of the neural tube defects (NTDs) had AF-AFPs in the 5.0-9.9 and 36 per cent in the > or = 10.0 MOM range. After a positive acetylcholinesterase (AChE) test, both the moderately and the very elevated groups had abnormalities in > or = 95 per cent of cases, compared with 85 per cent in the mildly elevated group. After a negative AChE test, abnormalities occurred in 79, 52 and 18 per cent in the very elevated, moderately, and mildly elevated groups, respectively. Excluding chromosome abnormalities, an abnormal twin, and bloody samples, the risk of a fetal abnormality after a normal ultrasound was less than 1 per cent if the AChE was positive in both the moderately and the very elevated groups. If the AChE was negative, the risk was 18 per cent for the moderately and 55 per cent for the very elevated groups, of which congenital nephrosis accounted for 75 per cent; AFP levels usually increased in a later AF sample. Repeat amniocentesis may be offered to women with AF-AFPs > or = 5.0 MOM if no abnormality is seen with high-resolution ultrasound.

Progressively since 1982 and as part of a nationwide programme for the diagnosis and prevention of genetic diseases, maternal serum alpha-fetoprotein (MS-AFP) screening and ultrasound fetal monitoring has been implemented in all pregnant women in Cuba. In Havana City, 328,983 pregnant women underwent MS-AFP screening between 15 and 19 weeks of gestational age. With a cut-off level of > or = 2 multiples of the normal median (MOM), 1767 amniocenteses were carried out to determine the levels of amniotic fluid AFP and 685 malformed fetuses were diagnosed. By ultrasound fetal monitoring, an additional 686 malformed fetuses were detected. As a result of the programme, the birth prevalence of neural tube defects has fallen by 90 per cent.

Aim: The value of the antenatal maternal serum screening by triple test during second trimester pregnancy has been examined for the Luxembourg population., Subject: In collaboration with the gynaecologists using our triple test, the performance of the screening has been evaluated against the outcome (before and at birth) of all the pregnancies screened between end of 1991 and 28.02.1996. In particular, the effectiveness of Down's syndrome (Trisomy-21) detection has been ascertained., Results: A total of 6760 pregnancies has been screened. Women's age ranged from 16 to 44 years, with a mean age of 28.4 years, 5.68% had > or = 35 years. The screening has been positive (at higher risk) for 7.25% pregnancies, wherein 5.98% were at higher risk for Trisomy-21 and 1.27% at higher risk for Neural Tube Defects (NTD). Among the screen positives, 20.79% were aged > or = 35 years and 79.21% were < 35 ans. There have been 12 Down's cases present among the 6760 pregnancies, 9 of them had in the screening a calculated risk higher than the cut-off (1:250). The detection rate (sensitivity) for Trisomy-21 was 75%, the specificity was 94.15% and the predictive value of a positive test was 2.23%., Conclusion: This study shows that our antenatal maternal serum screening compares favorably with the other screenings realized by reference centres and the results produced are reliable.

The authors examined the impact of prenatal diagnosis and elective termination of neural tube defect (NTD)-affected pregnancies on NTD prevalence and risk estimates. Prevalence data were actively ascertained and were derived from a population-based 1989-1991 cohort of California births. Included were 664 singleton infants/fetuses with an NTD. The birth prevalence (livebirths and stillbirths only) was 48.4% of the total prevalence (including elective terminations) for anencephaly and 70.2% for spina bifida. The authors also used in-person interview data from mothers of 538 of the ascertained NTD cases and mothers of 539 randomly selected nonmalformed control infants to examine maternal/infant characteristics. Compared with women who delivered liveborn/stillborn infants with an NTD, women who electively terminated NTD-affected pregnancies were disproportionately white, were more highly educated, had higher incomes, and used vitamins containing folic acid more often. For factors associated with elective terminations, risk estimates appeared biased when only liveborn and stillborn infants were included among cases compared with analyses in which all clinically recognized NTD-affected pregnancies were included.

Active and passive surveillance methods were utilized in an attempt to identify all neural tube defect (NTD)-affected pregnancies in South Carolina, a state previously identified to have a high prevalence of these defects (Greenberg et al., 1983). Sources of case ascertainment included maternal serum alpha-fetoprotein (MSAFP) programmes, prenatal diagnosis (amniocentesis) programmes, physician offices, perinatal centres, hospital medical record departments, and vital records. One hundred and nine NTD cases were identified over 24 months, indicating a prevalence of 1.60 cases per 1000 recorded births and fetal deaths (surveillance 1 October 1992-30 September 1994). Fifty-three (49 per cent) of the 109 NTD-affected pregnancies were either spontaneously or electively aborted prior to 26 weeks' gestation. Only three (6 per cent) of these early termination NTD cases were recorded in vital records, while medical records recorded 40 cases (75 per cent). By monitoring MSAFP programmes and maintaining frequent contact with physician offices and perinatal centres, 85 per cent of these early termination NTD-affected pregnancies were identified. However, for complete ascertainment of NTD-affected pregnancies, the utilization of all of these ascertainment methods was necessary, as each ascertainment method identified NTD cases missed by the other methods. Consideration of the significant impact of prenatal diagnosis on NTD surveillance and the use of multiple ascertainment methods in an attempt at complete ascertainment is particularly important now because of the recent recommendation for the periconceptional use of folic acid to prevent neural tube defects and the need for epidemiological studies to monitor the effectiveness of this prevention.

Objective: To determine the impact of prenatal diagnosis on the birth prevalence of neural tube defects (NTDs) in Atlanta during 1990 through 1991., Methods: Live-born and stillborn infants with NTDs who were at least 20 weeks' gestation were ascertained by the Metropolitan Atlanta Congenital Defects Program (MACDP), a population-based birth defects registry. Prenatally diagnosed NTD-affected pregnancies were ascertained from the four perinatal centers and the three genetic laboratories operating in Atlanta during 1990 through 1991. Fetal death certificates were also reviewed for potential cases., Results: During 1990 through 1991, MACDP ascertained 59 NTD cases, for a birth prevalence of 0.77/1000 live births. During this period, an additional 28 NTD-affected pregnancies were detected prenatally and terminated before 20 weeks' gestation. The adjusted NTD rate during 1990 through 1991, which includes prenatally diagnosed cases, was 1.13/1000 live births., Conclusions: Prenatal diagnosis is making a substantial impact on the birth prevalence of NTDs in Atlanta. However, since NTD rates in Atlanta were 2 to 2.5 per 1000 live births in 1970, prenatal diagnosis and termination of pregnancy does not completely account for the declining rate of NTDs.

Maternal serum alphafetoprotein (MSAFP) screening has been set up in Asturias, in the north of Spain, in 1987 in order to make possible the prenatal diagnosis of neural tube defects (NTD) to overall pregnancy population. This large study shows the high sensitivity and specificity of MSAFP screening when it is done with absolute control of all variables such as gestational age, pregnant woman's weight, diabetes, etc. On the other hand, this study also shows a poor sensitivity second level ultrasound for the early diagnosis of NTD in the presence of spina bifidas with no bulge. We have also observed that the incidence of NTD in Asturias remained constant in the last six years, around 1.5-1.6 per 1000 pregnancies. However, due to MSAFP screening, there has been a decline in the prevalence of children born with these defects. We conclude that MSAFP screening is the best tool to identify and reduce NTD in our Region (Spain).

Prenatal screening for Down's syndrome (DS) can be achieved by combining maternal age risks and maternal serum additional parameters (AFP, HCG, uE3) by computer assisted statistical analysis. Nevertheless this measure of risk is far from broad and practical application in Italy, due to cultural and organization difficulties. So we suggest a different technical approach, the age specific risk being multiplied by the HCG/AFP likelihood ratio. HCG and AFP can be tested by an automated Elisa assay, and calculations performed by a simple method, excluding computer and software package use. About 100 pregnancies were evaluated both by a modified version of the Wald test and the method described hereafter. Using the automated HCG and AFP Elisa Testing and Crossley statistical calculation a higher False Positive Rate was observed. On the other hand no different Detection Rate was observed for the two tests. On a retrospective study we found that 5 sera from affected pregnancies were correctly identified both by the modified Wald test and the other method. It is concluded that, despite different False Positive Rates, the choice of which test to use depends on evaluation of local resources, one test being easier-to-perform and more sensitive, the other one probably being more specific but more difficult to perform.

Screening for genetic abnormalities is an integral part of obstetrics. Prior to initiating screening, however, several prerequisites must be met: (i) capacity to alter clinical management, (ii) cost effectiveness, (iii) reliable means (usually assays) of assessment, and (iv) capacity to handle problems. In all pregnancies one should determine in systematic fashion whether family history places a pregnant woman at increased risk over the background risk of 2-3% congenital anomalies. All women over age 35 years at delivery should be offered prenatal cytogenetic testing, and women of all ages should be offered maternal serum alpha-fetoprotein screening for neural tube defects. Screening ostensibly normal populations is appropriate in certain ethnic groups to determine heterozygosity for selected disorders: Blacks for sickle-cell anaemia, Mediterranean people for beta-thalassaemia, Southeast Asians and Filipinos for alpha-thalassaemia, Ashkenazi Jews and perhaps French-Canadians for Tay-Sachs disease. Cystic fibrosis screening (delta F508 mutations) is not currently recommended for the general populations, but should be offered to relatives of an individual having delta F508 cystic fibrosis. Irrespective of the extent of screening programmes for Mendelian traits, the mutant allele will remain in the general population because by far the greatest genetic load lies in clinically normal heterozygotes, affected contributing far less to the load despite the obvious clinical effect.

Study Objective: The aims were (1) to determine whether in Europe, 1980-86, geographical differences in total prevalence of neural tube defects persist; (2) to examine the stability of total prevalence rates over time; (3) to evaluate the impact of prenatal diagnosis in terms of frequency and timing of termination of pregnancy., Design: Prevalence rates of neural tube defects were determined from case registration data in 20 EUROCAT regional registers of congenital anomalies, 1980-86. The chi 2 test for homogeneity in proportions was used to test whether differences in total prevalence rates were significant between regions or over time., Setting: Geographically defined populations were used in the Republic of Ireland, United Kingdom, Belgium, The Netherlands, Luxemburg, Denmark, France, Italy, Yugoslavia, and Malta., Patients: The patients were 3113 cases of anencephaly, spina bifida, encephalocele, and iniencephaly. Total cases (livebirths, stillbirths and induced abortions following prenatal diagnosis) were registered in 14 regions. Induced abortions were excluded from registration in six regions., Measurements and Main Results: Total prevalence rates (including livebirths, stillbirths and induced abortions) were 24 to 38 per 10,000 in six areas of Ireland and United Kingdom. Average total prevalence rate in eight continental European areas was 11.5 per 10,000. There was a secular decline in total prevalence in Dublin (Republic of Ireland) and Northern Ireland (United Kingdom) and a fluctuation in Glasgow, Liverpool, and South Glamorgan (United Kingdom). Total prevalence in continental Europe was stable over time. There was no significant geographical or secular variation in the spina bifida to anencephaly ratio (1.3). The ratio of encephalocele to other neural tube defects was lower in the British Isles (0.09) than in continental Europe (0.18). The impact of prenatal diagnosis and termination of pregnancy is increasing over time. Terminations were performed 1984-86 in at least 80% of total cases of anencephaly in 6/11 centres registering induced abortions, and in at least 40% of total cases of spina bifida in four centres. Serum alpha fetoprotein screening in British centres was associated with earlier prenatal diagnosis of spina bifida than ultrasound screening in other centres., Conclusions: Geographical and secular variation in total prevalence of neural tube defects persists in Europe 1980-86, independent of the practice of prenatal diagnosis. There is considerable regional variation in the impact of prenatal diagnosis in terms of frequency and timing of diagnosis and pregnancy termination linked to different policies and practices of prenatal screening.

The UK Northern Region Fetal Abnormality Survey was notified of 572 suspected fetal abnormalities in 1987. Of these, 265 (46%) had pediatric surgical implications. Because the registry traces the postnatal outcome of each notification and records congenital abnormalities diagnosed postnatally, it is possible to measure both sensitivity and selectivity of antenatal diagnosis of fetal abnormalities. Cases were divided into five groups: diaphragmatic hernia, abdominal wall defects, intestinal anomalies, neural tube defects, and urological anomalies. Each group comprised cases that were unsuspected, suspected but not confirmed, and suspected and confirmed. Sensitivity was highest in the urological group, but 30% of the notified cases were unconfirmed so selectivity was higher in the abdominal wall and neural tube groups. None of the diaphragmatic hernias and only 14.3% of the intestinal anomalies were correctly suspected. Only 13.5% of all neural tube defects were treated surgically. The Survey has improved cooperation and communication between specialists concerned with the management of fetal abnormalities and this in turn has improved patient care.

Experience with the diagnosis of neural tube defects from alpha1-fetoprotein (AFP) concentrations in amniotic fluid is reported from a prospective study of five laboratories testing for 13 Canadian genetic centres. The results of the study indicate that antenatal diagnosis of open neural tube defects is being carried out effectively in Canada (in 99.2% of cases the AFP measurements were interpreted correctly). Amniocentesis should be recommended to women at high risk for having a child with a neural tube defect (i.e., those who have a child, a parent or a sibling with a neural tube defect). The rate of neural tube defects in 182 high-risk pregnancies was 2.2% for an open defect and 1.1% for a closed defect, whereas the rate in 673 pregnancies in which amniocentesis was being performed for other reasons was 0.3%. This suggests that the AFP concentration should be measured in any sample of amniotic fluid collected for other reasons (usually fetal karyotyping). There were three instances of false-negative results, for a rate of 0.4%. Two closed neural tube defects were not detected; this limitation of the test has also been found by others. One of the six fetuses with an open neural tube defect, who died in utero, had a large myelocele in the neck that was not recognized. There were also four instances of false-positive results, for a rate of 0.5%. The findings suggest that AFP values that are more than 2 but less than 7 standard deviations (SDs) above the mean may indicate a neural tube defect, and that values 7 or more SDs above the mean very likely indicate such a defect, although other reasons for such high values (e.g., fetal erythrocytes in the amniotic fluid, intrauterine death and mistaken gestational age) must be ruled out by other methods.

Maternal serum alpha-fetoprotein (AFP) estimation as a routine screening test for neural tube defect (NTD) was introduced into the West Berkshire Health District, where 17 per cent of all deliveries and most of the antenatal care is undertaken by the general practitioners. In the first year, 4458 patients were screened and 43 of those (0.96 per cent) had raised serum AFP levels. Amniocentesis was performed on 31 patients (0.69 per cent). Ten fetuses with severe NTDs and one with exomphalos were detected and the pregnancies terminated. In six patients, raised serum AFP levels were due to fetal death. No normal pregnancy was terminated. Acceptability by patients was high. Provided that a good diagnostic ultrasound facility is available locally, maternal serum AFP estimation seemed to be a valuable screening test.

High resolution diagnostic ultrasound was assessed as a screening method for craniospinal anomalies during the second trimester of pregnancy in a population at low risk for neural tube defects (83,403 mothers). The effectiveness of the test was about 60% and the failure rate mainly due to late attendance. In a subgroup (9325) where the screening purposes were satisfactorily fulfilled, the detection rate (87%) was substantially greater. The significance of the results and the cost/benefit ratio, especially compared with serum alpha-feto protein screening services, are then discussed.

In Cuba and in the German Democratic Republic (GDR) a total of 24,412 pregnant women were tested for maternal serum alpha-fetoprotein (MSAFP) at the 16th to 20th week of gestation. An inexpensive and partly automated ultramicroliter enzyme immunoassay (ELISA) with final volumes of 10 microliter was used to analyze simultaneously 50 samples. The intraassay coefficient of variation (CV) of 5-8% and day/day CVs of 6-10.5% were obtained with a test frequency of 320 assays/day. A cut-off level of twice the median value (MoM) was chosen. An amniocentesis was done in a total of 0.5% (in the GDR) and 0.7% (in Cuba) of the screened women. The prevalence of open neural tube defects (ONTD) was calculated from the present study and was 1.43% in Cuba and 1.34% in the GDR. Through MSAFP screening 88.2% ONTD were detected. There was no therapeutic abortion of a normal fetus. The approximate cost for this program was about 2.36 marks-GDR per patient screened, or about 2,048 marks per ONTD detected.

Neural tube defects, anencephaly and spina bifida (including encephalocele) have been the major malformation problem in South Wales. Births of affected offspring of residents of Mid and South Glamorgan between 1956 and June 1985 were ascertained from various sources. To these were added terminations following prenatal diagnosis and affected spontaneous abortions of 16 weeks gestation or more since 1973. Variable fluctuation in prevalence occurred between 1956 and 1965. Since then there has been an accelerating decline in the birth prevalence of NTD but especially of anencephaly in both counties. When abortions and terminations are taken into consideration the decline until 1984, though still present, is much slower and is virtually non-existent now. The need for continuing NTD pregnancy screening and prenatal diagnosis followed by selective abortion is stressed. It is suggested that genetic counselling health education to improve maternal nutrition preconceptional counselling and population folic acid supplementation should be extended to prevent these defects.

A survey was carried out to determine the effect of prenatal screening and therapeutic abortion on births in 1985 with anencephaly and spina bifida in England and Wales. Maternal serum alpha-fetoprotein tests were done on 399,288 women (60 per cent of pregnant women): 4 per cent were reported as being screen-positive and 1 per cent had an amniocentesis. An estimated 534 pregnancies associated with anencephaly were terminated and an estimated 445 pregnancies associated with spina bifida (but without anencephaly) were terminated. Most (63 per cent) of the anencephalic pregnancies were first suspected from an ultrasound examination; 57 per cent of the spina bifida pregnancies were first suspected from a positive maternal serum alpha-fetoprotein test, 35 per cent by ultrasound, and the remaining 8 per cent by other means. The birth prevalence of anencephaly declined by 94 per cent between 1964-1972 and 1985, but when the terminations of pregnancy on account of having a fetus with anencephaly are added to the births the decline in prevalence was only 50 per cent. The birth prevalence of spina bifida declined by 68 per cent over the same period but when the terminations were added to the births the decline in prevalence was only 32 per cent. Among births with anencephaly 66 per cent had had no screening or diagnostic tests in early pregnancy, but in those that did nearly all were positive--usually in twin pregnancies where one fetus was affected but not the other. Among births with spina bifida, 48 per cent had no tests and in those that did the results were mainly negative.(ABSTRACT TRUNCATED AT 250 WORDS)

An evaluation was made of all cases of neural tube defects born in seven gynaecological hospitals and obstetric centres of Havana, between 1970 and 1980. Neural tube defects were recordable from 492 infants out of 319,228 births. The families concerned were briefed in human genetics and informed about the possibility of prenatal diagnosis of anencephaly and bifid spine (spina bifida aperta). Some of them had a record of this defect. Amniocentesis was applied to 30 women with an empirical risk of 1:20, and alphafoetoprotein was analysed in their amniotic fluid. Anencephaly was diagnosed in one case and confirmed by termination of pregnancy. The occurrence of neural tube defects usually is of spontaneous nature, and incidence is relatively high. Therefore efforts are now being made to introduce a scheme of prenatal screening based on alphafoetoprotein assessment in the serum of pregnant women.