The effect of Rhesus status on first‐trimester pregnancy screening markers free β human chorionic gonadotropin, pregnancy‐associated plasma protein‐A and nuchal translucency

Abstract

To examine whether maternal Rhesus status has any effect on the levels of first-trimester markers free beta-human chorionic gonadotropin (beta-hCG), pregnancy-associated plasma protein-A (PAPP-A) and nuchal translucency (NT). First-trimester free-beta-hCG and PAPP-A levels from pregnant women attending three hospitals in Kent were converted into MoMs and corrected for maternal weight, ethnicity, and smoking status. Maternal Rhesus status data were merged with screening data and free-beta-hCG and PAPP-A medians multiples of medians (MoMs) and NT from the Rhesus positive and Rhesus negative group were compared. Totally, 15 045 normal, singleton pregnancies were retrieved with full records. Altogether, 16.0% of the population were Rhesus negative. There was no difference between the medians MoMs of both free-beta-hCG nor PAPP-A nor NT in the two Rhesus status groups (p > 0.05). Demographic analysis on the distribution of Rhesus status in different ethnic origins showed that Caucasians have lower percentages of RhD-positive antigen compared to Asians and Afro-Caribbeans. Maternal Rhesus status does not influence the levels of free-beta-hCG and PAPP-A in the first trimester of pregnancy in this almost exclusively Caucasian population studied; therefore correction for maternal Rhesus status is not suggested.