First trimester maternal serum pregnancy-associated plasma protein A and pregnancy-specific beta 1-glycoprotein in fetal trisomies

Abstract

Objective: To examine the potential value of maternal serum levels of pregnancy-associated plasma protein A (PAPP-A) and pregnancy-specific beta 1-glycoprotein (SP1) in the detection of fetal trisomy.

Design: Cross-sectional study.

Setting: The Harris Birthright Research Centre For Fetal Medicine, King's College Hospital Medical School, London, UK and Division of Maternal-Fetal Medicine, Jefferson Medical College, Philadelphia, USA.

Subjects and methods: Maternal serum PAPP-A and SP1 concentrations were measured at 10 to 13 weeks gestation in samples from 42 pregnancies with fetal trisomy (trisomy 21, n = 29; trisomy 18, n = 9; trisomy 13, n = 4) and in samples from 210 matched controls.

Results: In controls, both maternal serum PAPP-A and SP1 increased significantly with gestation and in trisomic fetuses levels of both hormones were reduced. However, discriminant analysis demonstrated that SP1 did not contribute significantly in the distinction between trisomic and control pregnancies. Although levels of PAPP-A were reduced throughout the gestational range examined (10 to 13 weeks), especially in cases with fetal trisomy 21, the deviation was more pronounced at 10 to 11 weeks than at 12 to 13 weeks gestation. In 45% of pregnancies with fetal trisomy 21 and 70% of pregnancies with trisomies 18 or 13 maternal serum PAPP-A levels at 10 to 11 weeks gestation were below the 5th centile of the normal range.

Conclusion: Maternal serum PAPP-A concentration in the first trimester of pregnancy may prove to be useful in the prediction of risk for fetal trisomies.