Correlation of Maternal Age, Weight, Pregnancy - associated Plasma Protein A, Free Beta-human Chorionic Gonadotropin, Fetal Crown-rump Length, and Fetal Gender with Fetal DNA Fraction in Non-invasive Prenatal Testing: An Experiment on Iranian Pregnant Women

Non-invasive prenatal testing (NIPT) as a novel screening method has been widely proposed to screen for common fetal chromosomal aneuploidies. The aim of the present study was to examine the possible effects of maternal age, maternal weight, fetal crown-rump length (CRL), serum pregnancy-associated plasma protein A (PAPP-A), free beta-human chorionic gonadotropin (free β-hCG), and fetal gender on cell-free fetal DNA (cffDNA) percentage fluctuations.

In the present cross-sectional study, 308 singleton pregnant women aged 20-47 years at 11+0 to 13+6 weeks of pregnancy referring to the DeNA Laboratory in Tehran, Iran, for NIPT test during a one-month period between July 2018 and August 2018 were selected randomly. The cffDNA was extracted from maternal plasma. Whole exome sequencing by a ion semiconductor sequencer using cffDNA was applied for all participants. The PAPP-A and free β-hCGas biochemical biomarkers were assessed using a closed chemilumine scence immunoassay analyzer. The Shapiro-Wilk test, Pearson analysis, beta regression analysis, and Mann-Whitney U test were performed to analyze the data.

In the screening population, the cffDNA percentage showed no significant correlation with CRL and maternal age (P=0.096 and P=0.881, respectively). However, the cffDNA percentage correlated well with maternal weight, PAPP-A, and free β-hCG (P=0, P=0.009, and P=0.001, respectively). Beta regression between cffDNA percentage and maternal weight, free β-hCG, and PAPP-A was significant (P<0.001). The mean cffDNA percentage between male and female fetal groups showed a significant difference (P<0.001).

This study demonstrated that the cffDNA percentage in the first trimester of pregnancy had a negative correlation with maternal weight and a positive correlation with PAPP-A and free β-hCG values. Furthermore, the cffDNA percentage in male fetuses was higher than that in female fetuses.