Maternal serum human chorionic gonadotrophin and pregnancy-associated plasma protein A in twin pregnancies in the first trimester

Objectives To determine the levels of free β‐human chorionic gonadotrophin (β‐hCG) and pregnancy‐associated plasma protein A (PAPP‐A) in twin pregnancies in the first trimester. Methods Serum samples were obtained from 67 pregnant women with twin pregnancies and maternal serum free β‐hCG and PAPP‐A concentrations were compared with those of 4279 singleton controls between the 8th and 13th weeks of gestation. Results The geometric means of chromosomally normal twin pregnancies were 1.85 MoM for free β‐hCG and 2.36 MoM for PAPP‐A. There were no cases affected by Down syndrome in either group. Conclusion Twin pregnancies secrete more PAPP‐A than expected on the basis of singleton controls whereas free β‐hCG production is not increased. The results of the present study can be used to establish normal reference values when introducing first trimester Down syndrome screening in prenatal care. Copyright © 2002 John Wiley & Sons, Ltd.