First trimester screening for Down syndrome and assisted reproduction: no basis for concern

In pregnancies obtained after assisted reproduction the false-positive rate or second trimester Down syndrome (DS) screening is increased by 1.5-3-fol d. This may cause an increase in the number of amniocenteses and the fetal loss rate. The present study for the first time examined whether assisted r eproductive technologies affect the results of first trimester screening. T he markers PAPP-A, free beta -hCG and the nuchal translucency (NT) thicknes s were examined at 12-14 weeks' gestation. Screening markers in 47 in vitro fertilisation (IVF), 63 ovulation induction (OI) and 3026 spontaneously co nceived singleton pregnancies were compared. The MoM (multiples of the medi an) value in the IVF pregnancies was 1.02 (95% CI: 0.85-1.22) for PAPP-A. 1 .14 (95%, 4, CI: 0.95-1.37) for beta -hCG and 0.97 (95% CI: 0.89-1.05) for NT, the MOM value in the of pregnancies was 0.89 (95% CI: 0.76-1.05) for PA PP-A. 1.08 (95% CI: 0.93-1.25) for beta -hCG and 1.02 (95% CI: 0.95-1.11) f or NT. The first trimester marker values in assisted reproductive pregnanci es and spontaneously conceived pregnancies were not significantly different . Estimated false-positive rates for a risk cut-off of 1:400 varied from 4. 7% in IVF pregnancies to 5.1% in OI pregnancies. Therefore the false-positi ve rate in Down syndrome screening should be independent of the method of c onception. Copyright (C) 2001 John Wiley & Sons, Ltd.