Maternal midtrimester serum AFP and free beta-hCG levels in in vitro fertilization twin pregnancies

We aimed to compare the levels of alpha-fetoprotein (AFP) and free beta-hum an chorionic gonadotrophin (beta-hCG) levels as multiples of the median (Mo M) values between spontaneous and in vitro fertilized (IVF) twin pregnancie s. The control group of spontaneous singleton pregnancies was used for calc ulating the gestational age specific median levels of the values. Within a cohort of 19 310 pregnancies, 145 twin pregnancies were identified. The dat a were collected from Down syndrome (DS) screening programmes in four Unive rsity catchment areas in Finland between 1994-98. Maternal midtrimester ser um marker levels were measured across gestational weeks 14-18. There were n o fetal chromosome anomalies in either of the twin groups or the singleton group. Serum AFP of 145 and beta-hCG values of 39 spontaneous twin pregnanc ies were compared to the values of 6548 singleton pregnancies. In IVF twins 30 AFP and 39 beta-hCG values were compared to the levels of the control g roup. Both AFP and beta-hCG values were twice as high in the spontaneous tw in pregnancies (medians 2.18 and 1.83 MoM respectively) as in the singleton group (medians 1.00 and 1.00 MoM respectively). In IVF twin pregnancies be ta-hCG levels were higher (median 2.20 MoM) than in spontaneous twins (p = 0.08), whereas no significant difference was found in AFP levels (2.30 MoM) . In conclusion, the higher levels of beta-hCG levels in IVF twin pregnanci es should be considered in DS screening to avoid high false positive rates. Copyright (C) 2000 John Wiley & Sons, Ltd.