Changes of Cell-Free Fetal DNA in Maternal Plasma after Elective Termination of Pregnancy

Abstract

Fetomaternal hemorrhage (FMH) during pregnancy or subsequent isoimmunization, caused by a breach of the placental barrier, could lead to an adverse perinatal outcome (1)(2). However, concerns have been raised regarding the accuracy of the standard Kleihauer–Betke test to quantify FMH (3). In a previously published study, we explored the possibility of using cell-free fetal DNA (fDNA) in maternal plasma as a novel marker of FMH after surgical and medical elective first-trimester termination of pregnancy (TOP) (4). In our earlier study, pre- and posttermination blood samples were drawn at various time points relative to TOP. To adjust for this confounder, we retrospectively applied a mathematical model to the analysis of the data. Projected pretermination fDNA values were calculated based on the anticipated linear increase of fDNA during pregnancy. Adjusted posttermination fDNA concentrations were calculated based on the reported 16-min clearance rate of circulating fDNA after delivery (5). Adjusted posttermination fDNA concentrations were then compared with the projected pretermination concentrations. In the present study, we specifically enrolled only pregnant women in the first trimester undergoing elective surgical TOP. In addition, the pre- and posttermination blood samples were drawn on the same day with a controlled time interval between TOP and the posttermination blood collection. The concentrations of circulating fDNA were then analyzed along with pertinent clinical information to better understand the dynamics of circulating fDNA after TOP. This study was approved by the Institutional Review Boards at Tufts-New England Medical Center and Boston University School of Medicine. Pregnant women in the first trimester of pregnancy undergoing elective surgical TOP at Boston Medical Center were enrolled. Gestational ages were ascertained by ultrasonography and were expressed as postmenstrual days. Paired blood samples were obtained before and immediately after the termination procedure. The blood samples were centrifuged at 800 g , after …