Screening for trisomy 13 by fetal nuchal translucency and maternal serum free beta-hCG and PAPP-A at 10-14 weeks of gestation

In 42 cases of trisomy 13 at 10-14 weeks of gestation, compared with 947 co ntrols, the median multiple of the median (MoM) of maternal serum free beta -human chorionic gonadotrophin (beta-hCG) and pregnancy associated plasma p rotein A (PAPP-A) was significantly decreased (0.506 MoM and 0.248 MoM resp ectively), whilst fetal nuchal translucency was increased (2.872 MoM). In 3 8% and 71% of cases of trisomy 13 maternal serum free beta-hCG and PAPP-A w as below the 5th centile of the appropriate normal range for gestation and in 62% of cases the nuchal translucency was above the 95th centile. When co mbined together in a multivariate algorithm with maternal age, 90% of cases of trisomy 13 could be detected at a 0.5% false positive rate or 84% at a 0.1% false positive rate. We conclude that specific trisomy 13 risks should be part of developing risk algorithms combining maternal serum biochemistr y and nuchal translucency for use in first trimester screening alongside th ose for trisomy 21 and trisomy Is. Copyright (C) 2000 John Wiley & Sons, Lt d.