First-trimester screening for trisomy 21 in singleton pregnancies achievedby assisted reproduction

BACKGROUND: The possible effect of assisted reproduction on first-trimester screening for trisomy 21 was examined by fetal nuchal translucency thickne ss (NT), maternal serum free beta -human chorionic gonadotrophin (HCG) and pregnancy-associated plasma protein-A (PAPP-A), METHODS: Parameters were me asured at 11-14 weeks in 411 singleton pregnancies achieved by controlled o varian stimulation, including 220 that had undergone IVF, Results were comp ared with 1233 singleton pregnancies conceived spontaneously. RESULTS: In t he IVF pregnancies, the median fetal NT was not significantly different fro m that in controls, whilst the median free beta -HCG was significantly incr eased, and PAPP-A was significantly decreased. In the intracytoplasmic sper m injection group, fetal NT and free beta -HCG values were not significantl y different from those in controls, but PAPP-A was significantly decreased. In those pregnancies achieved by ovarian stimulation, neither fetal NT, fr ee beta -HCG nor PAPP-A were significantly different from the control group . CONCLUSIONS: In IVF pregnancies, screening for trisomy 21 by fetal NT, ma ternal serum free beta -HCG and PARE-A levels may be associated with a 1.2% higher false-positive rate than in natural conception.