Fetomaternal hemorrhage in the second trimester

Abstract

To investigate fetomaternal hemorrhage (FMH) rate and quantity in the second trimester of pregnancies with fetal anomalies and to assess the impact of invasive prenatal and termination procedures. Blood samples from women before termination of pregnancy were collected and analyzed by dual-color flow cytometry. Various clinical parameters were studied for their association with FMH. In total, 67 women were recruited; pre- and post-termination pairs were collected for 31 women. HbF cells were present in 91.0% of specimens, in 29.9% the transfused blood volume was ≥4.2 mL. FMH ≥30 mL was found in 3.0%, and chronic FMH, defined as FMH ≥40% of fetoplacental blood volume in 7.5%. At the limit of quantification (0.1%) none of the clinical parameters was associated with the presence of HbF cells, nor was there a difference in HbF cell concentrations between pre- and post-termination blood samples. Compared to normal term pregnancy, transfer of fetal red blood cells into the maternal circulation is increased in second-trimester pregnancies with fetal anomalies. FMH is not associated with invasive procedures or surgery performed in the context of termination. We hypothesize that the abnormal pregnancy itself, by means of an abnormal uteroplacental interface, is causing the increased transfer.