Comparing First Trimester Screening Performance: Routine Care Gynaecologists’ Practices vs. Prenatal Centre

Abstract

To evaluate and compare the screening performance for fetal trisomy 21 in the first trimester of pregnancy in general gynaecologists' practices and specialised centres for prenatal care in Germany. This study included 15,026 serum samples analysed in our laboratory for free beta-human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein-A (PAPP-A) at 11-14 weeks of gestation between 1.1.2000 and 31.12.2003. Fetal risk for trisomy 21 was calculated using nuchal translucency (NT) values and crown-rump-lengths (CRL), measured either in general gynaecologists' practices or in a tertiary level prenatal centre. The detection rate for a fixed risk cut-off (1:300) and a fixed false-positive rate (5 %) was calculated for NT, serum biochemistry, maternal age and the combination of these components. The estimated risk for trisomy 21 based on maternal age, fetal NT and maternal serum free beta-hCG and PAPP-A was 1 in 300 or greater in 5.1 % (362 of 6897) and 8 % (329 of 3840) of normal pregnancies, and in 78.9 % (15 of 19) and 88.5 % (23 of 26) of those with trisomy 21. For a fixed false-positive rate of 5 %, the respective detection rates of screening for fetal Down's syndrome by maternal age and serum free beta-hCG and PAAP-A, maternal age and fetal NT and by maternal age, fetal NT and maternal serum biochemistry were (general gynaecologists' practices/prenatal centre) 68.4/69.2 %, 42.1/65.4 % and 78.9/88.5 %, respectively. The screening results are satisfactory in both general gynaecologists' practices and a prenatal centre.