Pregnancy outcomes in nulliparous women with positive first-trimester preterm preeclampsia screening test: the Great Obstetrical Syndromes cohort study

Abstract

The Fetal Medicine Foundation proposed a competing risks model for early identification of women at a high risk of preterm preeclampsia, typically associated with deep placentation disorders. The Great Obstetrical Syndromes include a spectrum of pregnancy complications (preeclampsia, intrauterine growth restriction, preterm birth, late spontaneous abortion, and abruptio placentae) that are also associated with deep placentation disorders. This study aimed to estimate the rate of placenta-mediated pregnancy complications in nulliparous women with a positive first-trimester Fetal Medicine Foundation preterm preeclampsia screening test. We conducted a prospective cohort study of nulliparous women recruited at 11 to 14 weeks of gestation. Maternal characteristics, mean arterial blood pressure, levels of maternal serum biomarkers (pregnancy-associated plasma protein-A, placental growth factor, and soluble fms-like tyrosine kinase-1), and mean uterine artery pulsatility index were obtained to calculate the risk of preterm preeclampsia according to the Fetal Medicine Foundation algorithm. The predicted risks were dichotomized as a positive or negative test according to 2 risk cutoffs (1 in 70 and 1 in 100). The detection rate, false-positive rate, and positive and negative predictive values were calculated for placenta-mediated complications, including preeclampsia, small for gestational age (birthweight <10th percentile), fetal death, preterm birth, and a composite outcome, including any of the foregoing. The same analyses were computed for a composite of severe outcomes, including preterm preeclampsia, severe small for gestational age (less than third percentile), and fetal death. We included 4575 participants with complete observations, of whom 494 (10.8%) had an estimated risk of preterm preeclampsia of ≥1 in 70 and 728 (15.9%) had a risk of ≥1 in 100. The test based on a risk cutoff of 1 in 70 could have correctly predicted up to 27% of preeclampsia, 55% of preterm preeclampsia, 18% of small for gestational age, 24% of severe small for gestational age, and 37% of fetal deaths at a 10% false-positive rate. The test based on a cutoff of 1 in 100 could have predicted correctly up to 35% of preeclampsia, 69% of preterm preeclampsia, 25% of small for gestational age, 30% of severe small for gestational age, and 53% of fetal deaths at a 15% false-positive rate. The positive predictive value of a screening test for preterm preeclampsia of ≥1 in 70 was 3% for preterm preeclampsia, 32% for the composite outcome, and 9% for the severe composite outcome. Nulliparous women with a first-trimester positive preterm preeclampsia Fetal Medicine Foundation screening test are at a higher risk of both preterm preeclampsia and other severe placenta-mediated pregnancy complications. Approximately 1 woman of 10 identified as high risk by the Fetal Medicine Foundation algorithm developed at least 1 severe placenta-mediated pregnancy complication.