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Background: Noninvasive fetal aneuploidy detection by use of free DNA from maternal plasma has recently been shown to be achievable by whole genome shotgun sequencing. The high-throughput next-generation sequencing platforms previously tested use a PCR step during sample preparation, which results in amplification bias in GC-rich areas of the human genome. To eliminate this bias, and thereby experimental noise, we have used single molecule sequencing as an alternative method., Methods: For noninvasive trisomy 21 detection, we performed single molecule sequencing on the Helicos platform using free DNA isolated from maternal plasma from 9 weeks of gestation onwards. Relative sequence tag density ratios were calculated and results were directly compared to the previously described Illumina GAII platform., Results: Sequence data generated without an amplification step show no GC bias. Therefore, with the use of single molecule sequencing all trisomy 21 fetuses could be distinguished more clearly from euploid fetuses., Conclusions: This study shows for the first time that single molecule sequencing is an attractive and easy to use alternative for reliable noninvasive fetal aneuploidy detection in diagnostics. With this approach, previously described experimental noise associated with PCR amplification, such as GC bias, can be overcome.

Objective: To assess the impact of rapid aneuploidy detection (RAD) combined with fetal karyotyping versus karyotyping only on maternal anxiety and health-related quality of life., Methods: Women choosing to undergo amniocentesis were selected into group 1, i.e. receiving a karyotype result only (n = 132) or to group 2, i.e. receiving both the result of RAD and karyotyping (n = 181)., Results: There were no systematic differences in time of RAD combined with karyotyping versus karyotyping only in terms of anxiety (P = 0.91), generic physical health (P = 0.76, P = 0.46), generic mental health (P = 0.52, P = 0.72), personal perceived control (P = 0.91) and stress (P = 0.13). RAD combined with karyotyping reduced anxiety and stress two weeks earlier compared to karyotyping only., Conclusion: RAD as add-on to karyotyping reduces anxiety and stress in the short term but it does not influence overall anxiety, stress, personal perceived control, and generic mental and physical health when compared to a karyotype-only strategy.

Objective: To compare the experiences of women who received a screen-positive test result for Down syndrome after nuchal translucency screening or after biochemical screening in the first trimester of pregnancy in the Netherlands., Method: Semi-quantitative questionnaires were sent to 40 women with a screen-positive test result for Down syndrome in the first trimester of pregnancy: 20 had undergone nuchal translucency screening (NT group) and 20 had undergone serum screening (PAPP-A and free beta-hCG) (SS group). In all the cases, chorionic villus sampling (CVS) had not revealed any chromosomal abnormalities., Results: The major reason for undergoing the screening test in both groups of women was to be more reassured about the health of the baby. In the NT group, 5 out of the 20 women stated that they had suddenly been confronted with the NT measurement during the ultrasound examination without even being asked, or had been caught by surprise about the possibility. Together with two other women, they felt that at that stage they had been insufficiently informed about what the test meant. In the SS group, two women also held this opinion. In 10 out of the 20 women in the SS group, the positive-screening result had caused (a great deal of) anxiety. In the NT group, this proportion was as high as 18 out of the 20. Six of the women in the NT group mentioned that 'seeing the baby' had been an important factor in their decision to undergo CVS. Even after a favourable result of CVS, a proportion of the pregnant women were still feeling anxious about the health of their baby (5 women in the SS group and 12 in the NT group). Nevertheless, a large proportion of the women in both groups was pleased that they had undergone the screening test. Only a few of them stated that they would not choose the same screening test again in a future pregnancy., Conclusions: An unfavourable screening result after NT screening appeared to have a greater impact than an unfavourable result after serum screening. This might partly be explained by the ultrasound examination visualising the increased risk during NT screening. An additional important role may have been played by the fact that an abnormal NT screening result implies an increased risk of other disorders besides Down syndrome, which the women should be informed about beforehand. Several factors place special demands on the counselling prior to NT screening., (Copyright 2004 John Wiley & Sons, Ltd.)

Objective: To determine the knowledge of pregnant women about prenatal tests, and what tests they would choose if offered. Also, the preference of pregnant women for second-trimester or first-trimester screening was assessed., Patients and Methods: Pregnant women receiving antenatal care in a decentralized primary care system (n=80), and pregnant women that were offered a prenatal diagnosis at the Academic Medical Centre (n=195), were asked to complete a questionnaire., Results: The response rate was over 80%. Most women in both groups preferred a screening test for Down syndrome to be performed in the first trimester of pregnancy. A combination of nuchal translucency measurement and first-trimester serum screening was the option of choice. The screening possibilities for Down syndrome were less well known to the women in the low-risk group compared with the women in the high-risk group. The offer of a prenatal screening test would have been declined by more than 30% of women at low risk for carrying a fetus with Down syndrome., Conclusions: Our results show that women prefer screening for Down syndrome to be performed in the first trimester of pregnancy, using both serum and ultrasound tests. In women at low risk for Down syndrome the knowledge of prenatal screening methods was less, as well as the acceptance of prenatal screening being lower., (Copyright 2002 John Wiley & Sons, Ltd.)

Meta-analysis was used to calculate maternal serum marker distribution parameters for Down syndrome risk estimation in the first trimester. Data from 44 series were combined: relating to pregnancy associated plasma protein (PAPP)-A in 18, free beta human chorionic gonadotrophin (hCG) in 17, alpha-fetoprotein (AFP) in 26 and unconjugated oestriol (uE3) in 9. All levels were expressed in multiples of the normal median (MOM) for gestational age. Individual PAPP-A levels were available for 439 first and second-trimester Down syndrome pregnancies. The median MOM value increased with gestation: 0.35 at 6-8 weeks (31 cases), 0.40 at 9-11 weeks (197), 0.62 at 12-14 weeks (113) and 0.94 thereafter (98). A cubic regression equation was fitted so it could be estimated for each week of gestation. For the other markers the median value in Down syndrome was estimated from the weighted mean across all first-trimester series: 1.98 MOM for free beta-hCG in 579 cases; 0.79 MOM for AFP in 243 and 0.74 MOM for uE3 in 226. Variance-covariance matrices were calculated directly in unaffected pregnancies and from the difference between affected and unaffected pregnancies in Down syndrome. Based on these parameters we estimate that screening at 9-11 weeks with PAPP-A and free beta-hCG will yield a 64.6 per cent detection rate for a 5 per cent false-positive rate. Adding a third marker will increase detection to 66.6 per cent for AFP and 68.6 per cent for uE3; using all four markers it increases to 70.1 per cent. Routine ultrasound nuchal translucency measurement in addition to serum testing will increase the rates to 86.4 per cent, 87.2 per cent, 87.9 per cent and 88.3 per cent, respectively.

We determined the aneuploidy detection rate achievable by early pregnancy screening with pregnancy associated plasma protein (PAPP)-A, free beta human chorionic gonadotrophin (hCG) and ultrasound nuchal translucency (NT) measurement. Women having prenatal diagnosis were scanned, and a blood sample was taken and stored. Stored samples were tested and a total of 37 were found to have Down syndrome, 8 to have Edwards syndrome and 255 were controls. Results were expressed in multiples of the gestation-specific median (MOM) value in the controls after regression and, for the serum markers, maternal weight adjustment. In Down syndrome the medians were for PAPP-A 0.63 MOM (95 per cent confidence interval (CI) 0.45-0.87); free beta-hCG 1.88 MOM (1.33-2.66); and NT 2.34 MOM (1.70-3.22). Using these parameters the expected detection rate for a 5 per cent false-positive rate for different marker combinations were: 55.3 per cent for PAPP-A and free beta-hCG; 68.4 per cent for NT alone; and 84.6 per cent for PAPP-A, free beta-hCG and NT. The median values for Edwards syndrome were: 0.17 MOM for PAPP-A; 0.18 MOM for free beta-hCG; and 2.64 MOM for NT. Early pregnancy screening with the combined measurement of maternal serum PAPP-A and free beta-hCG and fetal nuchal translucency could achieve a high Down syndrome detection rate.

Objective: To assess the value of the triple test incorporating individual differences in parental evaluation of outcomes of pregnancy., Design: Decision analysis., Sample: Monte Carlo simulation of triple test results in 25,000 women with a normal pregnancy and 25,000 women with a pregnancy affected by Down's syndrome., Methods: A decision model was developed for women who were 16 weeks pregnant. Three strategies were evaluated: 1. no prenatal testing; 2. amniocentesis; and 3. the triple test followed by amniocentesis if the risk of a pregnancy with Down's syndrome, based on maternal age and the triple test results (post-test risk), was above the woman's threshold risk for amniocentesis., Main Outcome Measures: The outcomes considered were: 1. birth of a child without Down's syndrome; 2. birth of a child with Down's syndrome; and 3. pregnancy loss, either spontaneously, or as a result of termination. The values of these pregnancy outcomes were expressed on a disutility scale in units of 'lost pregnancy equivalents'. The birth of a normal child brings no disutility. The disutility of the birth of a child with Down's syndrome is consequently specified by the ratio of the expected parental distress after the birth of a child with Down's syndrome to the expected parental distress after the loss of the pregnancy (disutility ratio)., Results: The value of the triple test depends strongly on maternal age as well as on the individual evaluation of the outcome of pregnancy. The triple test is of considerable value for all women > 38 years; its value for women between 27 and 38 years depends on the disutility ratio, and it is of little value for women < 27 years., Conclusion: The value of the triple test depends on the parental evaluation of outcome of pregnancy for a large group of pregnant women. The disutility ratio, as introduced in this study, might be an instrument to elicit these values for individual women in clinical practice.

Objective: To examine the discriminative capacity of nuchal translucency measurement in the detection of trisomy 21 and other chromosomal anomalies., Design: Prospective cohort study., Subjects: A total of 2247 women with viable singleton pregnancies between 10 and 14 weeks' gestation attending a prenatal diagnosis center for fetal karyotyping., Methods: The fetal nuchal translucency was measured transabdominally in all women before invasive prenatal testing., Results: Chromosomal abnormalities were found in 63 fetuses, including 36 with Down's syndrome. The likelihood of the presence of chromosomal abnormalities increased with larger nuchal translucency thickness. A nuchal translucency of 3 mm or more identified 25 out of 36 fetuses (69%) with trisomy 21 at the expense of a 4.0% false-positive rate. Correction of nuchal translucency measurements for differences due to variation of the measurement with gestational age, either by using the 'delta-value' or multiples of the median (MoM), did not improve the detection rate in our patient data set., Conclusions: The discriminative capacity of nuchal translucency measurement makes it a useful tool in screening for trisomy 21 and other chromosomal anomalies.

Objective: To examine the effectiveness of nuchal translucency measurement in the detection of trisomy 21 in a low-risk population., Design: Prospective cohort study., Subjects: A total of 1473 women with viable singleton pregnancies between 10 and 14 weeks' gestation attending an antenatal clinic for routine obstetric care., Methods: The fetal nuchal translucency was measured in all women. Fetal karyotyping was performed for the usual indications and in cases of a nuchal translucency measurement > or = 3 mm., Results: Down's syndrome was found in nine fetuses (0.6%). Screening by maternal age would have diagnosed six out of nine fetuses (67%) with trisomy 21 for an invasive testing rate of 24%. Because the actual uptake of prenatal diagnosis for maternal age was 79%, only 44% of the Down's syndrome fetuses would have been detected prenatally by this screening method. A nuchal translucency of 3 mm or more identified 67% of the fetuses with trisomy 21, for an invasive testing rate of 2.2%. The combination of nuchal translucency thickness, corrected for the influence of gestation by 'delta-value' and maternal age performs differently according to the chosen cut-off point for adjusted risk. A minimum risk of 1 : 100 would detect 78% of the Down's syndrome fetuses for a testing rate of 8.1%. By offering karyotyping to all women with a post-test risk of 1 : 300, the detection rate would increase to 100% with an invasive testing rate of 19.8%. This is lower than the invasive testing rate of maternal age screening., Conclusions: These data suggest that nuchal translucency measurement is an effective screening method for trisomy 21 in an unselected obstetric population.

Serum concentrations of fetal antigen 2 (FA-2), the amino-propeptide of the alpha1 chain of collagen type I, were measured in peripheral blood from women with normal (n = 234) and trisomy 21 affected (n = 14) pregnancies between 9 and 11 weeks gestation. Serum FA-2 concentrations were seen to be stable throughout this period, and though raised FA-2 concentrations were seen at the 10th week of gestation, a statistically significant difference between normal and trisomy 21 affected pregnancies was not found overall. Therefore it seems unlikely that FA-2 has a role in first trimester screening for trisomy 21, despite the fact that significantly higher FA-2 concentrations in trisomy 21 and significantly lower concentrations in trisomy 18 had been previously demonstrated in amniotic fluid in the second trimester.

Objective: To examine if, and if so, in what way, the maternal serum screening for fetal neural tube defects (NTD) and Down's syndrome (DS) in the Dutch decentralized obstetrical organization would be feasible and effective., Design: Prospective., Setting: University Hospital Groningen., Method: Between October 1st 1990 and December 1st 1991 we determined the likelihood of a baby with a NTD and/or DS in 2580 pregnant women, at 15 to 20 weeks gestation, by serum screening., Results: Five foetuses with DS were detected, as well as two with a NTD, one foetus with an omphalocele, and one with Turner's syndrome. One infant with a NTD and one with DS were not found prenatally. Of all 98 women of 36 years or older, 68 declined amniocentesis because their risk was lower than the age related risk., Conclusions: Maternal serum screening for NTD and DS is feasible and effective in principle. In a decentralized prenatal care system, special attention has to be paid to the time needed to report the results and to the completion of the follow-up. The detection rate of DS in pregnant women of 36 years or older remains almost the same, but a significant number of them decline prenatal diagnosis. An increased risk of foetal DS, determined by serum screening, should be added to the official list of indications for prenatal diagnosis in the Netherlands.

We measured immunoreactive inhibin in the maternal serum of 80 pregnancies with a chromosomally normal fetus and ten Down's syndrome pregnancies in the second trimester. The inhibin level in all Down's syndrome pregnancies was above the normal median; the multiple of the normal median (MoM) was 1.9. We found a statistically significant difference between the levels of inhibin in unaffected and affected pregnancies (Kolmogorov-Smirnov test: p < 0.002). Using an arbitrarily chosen cut-off of 2.4 MoM, 40 per cent of Down's syndrome and 5 per cent of the normal pregnancies were found. We conclude that immunoreactive inhibin may be useful as a marker for fetal Down's syndrome.

The Dutch Working Party on Prenatal Diagnosis has initiated a study on the possibilities of first-trimester screening for fetal chromosomal disorders. We report on maternal serum human chorionic gonadotrophin (MS-hCG) measurements in 1348 pregnancies with a chromosomally normal fetus and 53 pregnancies with a chromosomally abnormal fetus. The median MS-hCG concentration in 24 pregnancies with Down's syndrome was 1.19 multiples of the normal median (MoM). The MS-hCG distributions in normal and Down's syndrome pregnancies did not differ significantly (t-test: t = 1.945, p greater than 0.05). We also found no difference between normal pregnancies and pregnancies with other chromosomal disorders (six cases of trisomy 18, MoM = 0.80; four cases of sex chromosome abnormality, MoM = 1.01; 17 cases of chromosomal mosaicism in chorionic villi, MoM = 1.11). Selecting an upper limit at the 90th centile could detect 25 per cent of pregnancies with Down's syndrome. We conclude that, in the first trimester, MS-hCG as a screening factor for Down's syndrome is of minor value. However, MS-hCG could be a useful factor in a first-trimester screening programme based on a combination of markers.