Antithrombin improves the maternal and neonatal outcomes but not the angiogenic factors in extremely growth-restricted fetuses at <28 weeks of gestation.

Severe preterm fetal growth restriction (FGR) remote from term is problematic. We aimed to investigate the effect of maternally-administered antithrombin on maternal and neonatal outcomes. A prospective, one-arm, pilot study was performed in 14 women with severe FGR (≤5th centile) at <28 weeks of gestation, without hypertensive disorders. Maternal plasma concentrations of soluble Feline McDonough Sarcoma (FMS)-like trypsin kinase-1 (sFlt-1) and placental growth factor (PlGF) were measured and categorized into three groups: group 1; low sFlt-1 and high PlGF, group 2; moderate sFlt-1 and low PlGF, and group 3; high sFlt-1 and low PlGF. Antithrombin was administered for 3 days. The incidence of perinatal mortality, infant morbidity, and the period of pregnancy prolongation were compared.In group 1 (n=4), their pregnancies were extended for longer periods and the maternal and infant outcomes were good. The prolongation periods were shorter in groups 2 (n=3) and 3 (n=7), which resulted in poor maternal [severe preeclampsia or hemolysis, elevated liver enzymes, and low platelet count (HELLP) syndrome] and infant outcomes.The evaluation of the maternal sFlt-1 and PlGF at 21-27 weeks of gestation is useful in the managements of severe FGR. Antithrombin treatment could prolong the pregnancies with low sFlt-1 and high PlGF without negatively affecting maternal or fetal health.