Circulating Fetal DNA in Maternal Plasma Is Increased in Pregnancies at High Altitude and Is Further Enhanced by Preeclampsia

Pregnancy at high altitude (>2700 m) is characterized by the delivery of smaller than average babies (birth weight may decrease by as much as 100 g per 1000 m increase in altitude), as well as an increased incidence of intrauterine growth restriction and preeclampsia (1)(2)(3). The placenta also exhibits clear morphologic changes, which may represent a compensatory adaptation to facilitate adequate transfer of oxygen to the fetus, in that the terminal villi display increased vascularization and thinning of the syncytiotrophoblast layer (4)(5).Previous studies have indicated that circulating fetal DNA concentrations in maternal plasma are increased in pregnancies affected by preeclampsia (6)(7), fetal growth restriction (8), or preterm labor (9); pregnancies with aneuploid fetuses (10)(11); and pregnancies affected by other pregnancy-related disorders involving an underlying placental pathology (12)(13). This has led to the suggestion that abnormalities in placentation may be associated with increased liberation of fetal DNA into the maternal circulation (14)(15).For this reason we investigated whether circulating fetal DNA concentrations are affected in pregnancies at high altitude. Furthermore, because it has also been reported that ethnic groups that have adapted to living at high altitudes for centuries or millennia, e.g., native Tibetans, have better pregnancy outcomes than recent migrants, e.g., Han Chinese (16), we examined samples obtained from ethnic Tibetans and …