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The purpose of our study was to assess the influence of intra-uterine insemination (IUI) on the results of maternal serum Down syndrome screening. 43 women with IUI pregnancies and 4507 healthy women who conceived were studied. Ovulation in IUI pregnancies was induced by clomiphene and/or human menopausal gonadotrophin (hMG). Maternal serum levels of free beta-human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP) were measured for Down syndrome screening. It was considered screen-positive when the risk of Down syndrome was 1 in 270 or greater in the second trimester. The value of maternal serum AFP was significantly lower in the IUI group (median=0.760 MoM) than in the control group (median=1.050 MoM). However, the value of free beta-hCG was not significantly different between the two groups. The positive rate of maternal serum Down syndrome in IUI pregnancies was similar to that of the control group. Our results indicate that IUI pregnancy may be associated with a lower level of AFP, although the mechanism for this difference remains unknown.

Background: The aim of this study was to ascertain the normal range of the midtrimester maternal urine alpha-fetoprotein (AFP) concentrations in Taiwanese pregnancies., Methods: AFP was measured in the urine samples, obtained before genetic amniocentesis, from 268 women with normal singleton pregnancies between 14 and 21 weeks of gestation. Week-specific median values for urine AFP/creatinine (Cr) were calculated by weighted linear regression after log transformation and the data were converted to units in the multiple of the median (MoM). The gestational age in all cases was determined by ultrasound parameters., Results: The levels of urine AFP and AFP/Cr increased gradually with advancing gestational age. The AFP/Cr MoM values of singleton pregnancies after log transformation showed a normal distribution with a mean (standard deviation) of 0.0071 (0.3228). The median, 10th and 90th centiles of AFP/Cr were 0.98, 0.43 and 3.61 MoM, respectively. Of the pregnant Taiwanese women studied, 4.9% (13/268) and 16% (43/268) had urine AFP/Cr MoM levels less than 0.31 MoM and 0.5 MoM respectively., Conclusion: The establishment of a reference range which allows for gestational differences in AFP/Cr levels is essential for further antenatal testing.

Background: This study was to determine the incidence of chromosome abnormalities in Taiwanese women undergoing prenatal chromosome analysis after a second trimester Down syndrome screening by using maternal age and serum dual-marker testing (alpha-fetoprotein and free-beta unit human chorionic gonadotropin)., Methods: A total of 10,098 Taiwanese women with pregnancy between 15 and 23 weeks' gestation received second-trimester Down syndrome risk evaluation by dual-marker and maternal age specific risk testing in a single medical center. The study took 22 months. Ninety-seven percent of this study population was less than 34 years old. Ninety-six percent of our cases were screened between 15-20 weeks of gestation. This population was included only after a routine ultrasonography scan for correction of gestational age and exclusion of major structural anomalies. By using an algorithm to detect Down's syndrome, with a risk of 1:270 as a cut-off value, 816 patients were screen-positive for Down syndrome (screen-positive rate 8.0%). Karyotypes were reviewed for 670 (82.1%) mothers who received prenatal karyotype analysis., Results: Twelve cases of Down syndrome were identified in the screen positive group with an estimated detection rate of 67% (false positive rate 8%). Three cases of Down syndrome were detected in late trimester among the screen-negative group. Seven other fetal chromosome abnormalities were also found among the screen-positive pregnancy. In addition, seven cases were screen-positive for trisomy 18; all of these patients received amniocentesis and only one case was confirmed., Conclusion: These findings indicate that this screening program combining alpha-fetoprotein (AFP), free beta human chorionic gonadotropin (free-hCG) and maternal age-specific would achieve a screening efficiency in Taiwanese populations as comparable to those obtained in Caucasian populations. Our results also suggest that approximately 3% of pregnancies with a positive dual marker and maternal age-specific screen results will have a chromosome abnormality despite having a normal routine ultrasound scan. Mothers with positive screening results should be made aware of the implications of a positive result.

Background: The purpose of this study was to assess the relation of maternal age and weight on the maternal serum alpha-fetoprotein (AFP), total human chorionic gonadotropin (hCG) and free beta-hCG levels during the second trimester., Methods: We collected 419 serum samples from normal singleton pregnancies to assay serum marker levels of AFP, total hCG and free beta-hCG between 14 and 21 weeks of gestation. Maternal age at the day of delivery and maternal weight at the time of sampling were recorded in all cases. The relationship between maternal weight and multiple of the median (MoM) levels of serum markers was analysed by regression models., Results: There was an inverse trend in median MoM levels of serum markers in relation to maternal weight. No significant association between maternal age and serum marker levels was found., Conclusion: Because of its impact on serum marker levels, weight correction may be mandatory for further refinement in the maternal serum screening for Down's syndrome.

High free beta human chorionic gonadotropin (beta-hCG) and low alpha-fetoprotein (AFP) levels were found in 47 Asian Down's syndrome pregnancies (median values 2.79 and 0.77 MOM, respectively). At a 5 per cent false-positive rate, free beta-hCG alone would identify 46.8 per cent of Down's syndrome pregnancies, age alone detected 34.5 per cent of affected cases, whilst AFP alone detected 17 per cent and free beta-hCG/AFP MOM ratios detected 48.9 per cent of Down's syndrome cases. When combined with maternal age-specific risk, free beta-hCG could achieve a 59.6 per cent detection rate, with AFP achieving 42.6 per cent, free beta-hCG/AFP MOM ratios 61.7 per cent, and combined free beta-hCG and AFP a detection rate of 63.8 per cent for a 5 per cent false-positive rate. Down's syndrome screening at an early gestational age (before 18 weeks) could achieve a 68 per cent detection rate with a 5 per cent false-positive rate, compared with a 59.1 per cent detection rate for a 5.2 per cent false-positive rate when screening at a late gestational age. The use of free beta-hCG in Down's syndrome screening programmes can yield an improved efficacy in the detection of Down's syndrome in an Asian population.

Maternal serum alpha-fetoprotein (MSAFP) screening has been widely used and proven valuable in the prediction of a variety of fetal disorders. Any laboratory intending to provide MSAFP screening needs to establish its own reference data. In order to establish a normal MSAFP median value at our own laboratory, 5256 samples of MSAFP were collected from uncomplicated, singleton pregnant women between 13 and 24 weeks' gestation. The MSAFP median levels steadily rise with advancing gestation about 16% per gestational week in average. There were 0.17% and 4.4% of the pregnancies with serum AFP levels less than 0.25 multiple of the median (MoM) and 0.5 MoM respectively, and 4.22% and 1.66% with serum levels above 2.0 MoM and 2.5 MoM. Accurate and satisfactory interpretation of MSAFP screening should be emphasized in the establishment of a well-developed normal median value.

To investigate the association between low amniotic fluid alpha-fetoprotein (AFP) and trisomy pregnancies, we retrospectively reviewed 26 trisomy pregnancies including 18 fetuses with Down's syndrome and eight with trisomy 18. The amniotic fluid AFP median values of Down's syndrome, trisomy 18, and the study groups were 0.73 MoM, 1.15 MoM, and 0.85 MoM, respectively. There was a significant difference between the mean values of the Down's syndrome-affected fetuses (0.78 +/- 0.29 MoM) and that of the control group (p < 0.001), whereas no such difference was found for that of trisomy 18-affected fetuses (1.16 +/- 0.38 MoM). Only three patients in the study group (3/26, 11.5%) had an amniotic fluid AFP value below 0.5 MoM, including the two cases of Down's syndrome (2/18, 11.1%) and one case of trisomy 18 (1/8, 12.5%). Most of the values for the trisomy pregnancies were within the normal range, thereby precluding the possibility of using this measurement as an alternative to fetal karyotyping as a screening test for Down's syndrome or other trisomy pregnancies.

To assess the relationship between alpha-fetoprotein (AFP) concentrations of amniotic fluid and maternal serum from 16 to 18 weeks' gestation, 890 paired samples of maternal serum and amniotic fluid were collected from women with normal singleton pregnancies. The gestational age was determined by ultrasonographic dating before amniocentesis, and the AFP measurements were performed by a single reference laboratory. There was a significant rise in the maternal serum AFP (MSAFP) concentration from 16 to 18 weeks' gestation. Amniotic fluid AFP concentrations significantly declined from 16 to 18 weeks' gestation. This study failed to demonstrate any statistical relationship between the AFP concentration of maternal serum and amniotic fluid (r = 0.031). This finding indicates that amniotic fluid AFP levels cannot be predicted by MSAFP levels between 16 and 18 weeks' gestation. Simple diffusion may not be the only mechanism for the transfer of AFP through the fetal membrane to maternal circulation.

An association between low maternal serum alpha-fetoprotein (MSAFP) and fetal trisomy has now been thoroughly documented. The mechanisms resulting in low MSAFP are still unclear. In order to determine whether the low values of MSAFP in autosomal trisomies are associated with smaller fetal weights, we compared 11 fetuses with Down syndrome (trisomy 21), 4 with trisomy 18, with 45 normal fetuses. All of them are aborted in the second trimester of pregnancy. No significant difference in the weight distribution between fetuses with Down syndrome and control fetuses was found. In contrast, as compared with the control fetuses, fetuses with trisomy 18 had a significant lower weight distribution. The mean value of MSAFP was 0.72 +/- 0.26 MoM for those with Down syndrome and 0.51 +/- 0.33 MoM for fetuses with trisomy 18; both results being significantly lower than that of normal control (1.01 +/- 0.28). The mean value of amniotic fluid AFP was 0.63 +/- 0.23 MoM for fetuses with Down syndrome. This value was significantly lower than those of the fetuses with trisomy 18 and normal controls (1.02 +/- 0.09 and 1.02 +/- 0.30). A linear relationship between MSAFP and fetal weight was found in normal fetuses at a given gestational age but was not found in trisomy pregnancy. Fetal weight cannot be used to explain the reason for low MSAFP in Down syndrome pregnancy but may partially account for the lower levels noted in fetuses with trisomy 18.