Is there an association between maternal ABO and rhesus blood groups and the first-trimester serum markers free beta-hCG and PAPP-A used for the detection of fetal aneuploidy?

Objectives: To evaluate whether first-trimester levels of PAPP-A and serum free-beta-human chorionic gonadotrophin (free beta-hCG) vary with maternal blood group and rhesus status and to assess whether this has implications for first-trimester screening for chromosomal anomalies.

Methods: Blood group and rhesus status information was extracted from birth records for women undergoing first-trimester screening. The birth records were combined with prenatal screening records by an in-house developed record linkage software. In 2252 singleton pregnancies of normal obstetric outcome, the median weight-corrected, ethnicity-corrected and smoking-corrected MoM were compared in the various blood groups, using t-tests after log10 transformation of the marker MoM against the whole study group.

Results: Only those women with a B rhesus positive blood group had statistically significant higher MoM levels of PAPP-A (0.995 v 0.937).

Conclusions: A larger study is required to establish the validity of this increase in PAPP-A in the B rhesus positive group. If this can be substantiated, the elevation in PAPP-A in this group may require correction when screening for chromosomal anomalies.