Screening for trisomy 21 by maternal age, fetal nuchal translucency and maternal serum biochemistry at 11–14 weeks: a German multicenter study

Abstract

Objective: To examine the effectiveness of screening for trisomy 21 by a combination of maternal age, fetal nuchal translucency (NT) thickness and maternal serum biochemistry using free β-humanchorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11-14 weeks of gestation.Methods: This was a multicenter study of screening for trisomy 21 by a combinationof maternal age, fetal NT and maternal serum free β-hCG and PAPP-A at 11-14 weeks of gestation, using the methodology developed by the Fetal Medicine Foundation. The distribution of estimated risksfor trisomy 21 was determined and the sensitivity and false-positive rate for a risk cut-off of 1 in 300 were calculated.Results: In total, 3864 singleton pregnancies with live fetuses at 11-14weeks were examined and the fetal NT and maternal serum free β-hCG and PAPP-A were successfully measured in all cases. The median maternal age was 33 (range 15-46) years and, in 1271 (35.8%), the agewas 35 years or more, the median gestation at screening was 12 (11-14) weeks and the median fetal crown-rump length was 64 (range 45-84) mm. The fetal NT was above the 95th centile in 73.7% (14 of 19) oftrisomy 21 and in 4.8% (169 of 3505) of normal pregnancies. The estimated risk for trisomy 21 based on maternal age, fetal NT and maternal serum free β-hCG and PAPP-A was 1 in 300 or greater in 6.6%(233 of 3505) of normal pregnancies, in 84.2% (16 of 19) of those with trisomy 21 and 88.9% (24 of 27) of those with other chromosomal defects.Conclusions: In Germany, the results of screeningfor chromosomal defects by measurement of fetal NT and maternal serum biochemistry, in centers with appropriately qualified sonographers, are similar to those reported in the UK using the same methodology.