Correlation of Fetal DNA and Human Chorionic Gonadotropin Concentrations in Second-Trimester Maternal Serum

The discovery of cell-free fetal DNA in maternal serum and plasma has opened a new avenue for noninvasive prenatal diagnosis and provided a useful marker of complicated pregnancy (1)(2)(3)(4)(5)(6)(7). In recent years, the analysis of fetal DNA in maternal serum or plasma has afforded successful prenatal diagnosis of fetal rhesus D status (2) and single-gene disorders (3), as well as fetal gender (4). In addition, an increased fetal DNA concentration in maternal serum or plasma has been demonstrated as a useful marker in preeclampsia (5)(6) and preterm labor (7). However, the origin of the fetal DNA and the biologic significance of its increase in complicated pregnancies remain unclear. Speculation as to the possible origin of fetal DNA has included the leakage of nucleated fetal cells into maternal circulation across the placenta or the direct release of trophoblast DNA into maternal circulation. Human chorionic gonadotropin (hCG), which is produced by trophoblasts and excreted directly into maternal circulation, is also reportedly increased in preeclampsia and preterm labor (8)(9)(10). The present study examined the association between fetal DNA and hCG concentrations in maternal serum by simultaneously measuring fetal DNA and hCG concentrations in healthy pregnant women.