Lower Maternal PLAC1 mRNA in Pregnancies Complicated with Vaginal Bleeding (Threatened Abortion <20 Weeks) and a Surviving Fetus

Trophoblastic cells of the placenta enter the maternal circulation and can be isolated there along with their specific mRNAs (1)(2). Increased concentrations of mRNA for corticotropin-releasing hormone, which is synthesized in the placenta, are seen in the blood of patients affected by preeclampsia (3), and panels of mRNAs(4) can be used to test for a disease of interest. The mRNA concentration in blood may vary with intracellular expression and with the number of trophoblastic cells expressing that specific mRNA per unit of blood. We hypothesize that pregnancies affected by a threatened abortion, but with a viable embryo, exhibit lower concentrations of mRNA for the placenta-expressed gene PLAC1 because of possible underlying delayed or abnormal placental growth at the time of maternal blood collection. We studied 10 pregnant women admitted for a threatened abortion at <20 weeks of gestation (threatened abortion group). The study was approved by our local ethics committee, and all patients gave informed consent. All fetuses with abnormal karyotypes and pregnant women with preeclampsia, pre- or postterm delivery, uterine pathology such as myomas or malformations, placenta abruptio, loss to follow-up, and a vaginal or cervical lesion visualized on clinical examination that could explain the vaginal bleeding were excluded from the study. We also excluded those women who had vaginal bleeding and a subsequent miscarriage because villus destruction, apoptosis, and embryo death could increase the number of circulating placental cells and nucleic acids in the maternal blood, as could abnormal fetal karyotype, fetal malformation, and abnormal maternal immune response. Placental abruption observed later in the pregnancy was also excluded as a possible source of feto-maternal hemorrhage. During hospitalization, all women were maintained at complete bed rest, and routine ultrasound examinations and endocrine (β-hCG) evaluation were carried out. We also studied 66 normal pregnancies as controls. All blood tests were performed 1–2 days after the first occurrence of bleeding.