In 1999, Lo and colleagues reported that the median fetal DNA concentration in maternal serum was
increased in women with established preeclampsia (PE) compared to controls [1]. Subsequently, several
other studies have confirmed this finding [2–5] which has been attributed to accelerated apoptosis of
trophoblastic cells resulting from placental ischemia [1] and reduced clearance of the cell free DNA from
the maternal circulation in women with PE [6]. There is also some evidence that cell free DNA and fetal fraction are altered in women who subsequently develop PE from the first trimester of pregnancy [7–13]. A recent large prospective study on 5,582 women at 12–20 weeks reported that fetal fraction was significantly reduced in women with PE compared to the unaffected preganncies [11]. Moreover, two other large prospective studies demonstrated that cell free fetal DNA and fetal fraction examined at 11–14 weeks were inversely related to uterine artery pulsatility index (UtA-PI) and mean arterial pressure (MAP) and had significant positive association with maternal serum pregnancy associated plasma protein-A (PAPPA) [14,15]. Furthermore, the study of Rolnik et al, showed that the risk of PE calculated by a combination of maternal factors, UtA-PI, MAP and maternal serum PAPP-A and placental growth factor (PLGF) [16], was inversely related to fetal fraction [15].
The aim of this study is to investigate first, whether first-trimester maternal plasma fetal fraction is altered in women that subsequently develop PE or gestational hypertension (GH) and second, its potential value in improving the performance of screening for PE and GH by maternal factors and maternal serum PAPP-A, MAP and UtA-PI.