LAUSR

INTRODUCTION Rates of some placental-associated pregnancy complications vary by ethnicity, though the strength of association with underlying placental pathology is presently unknown. Our objective was to determine whether an association between ethnicity and placental pathology occurs in low-risk pregnancies. METHODS 829 low-risk nulliparous pregnant women were prospectively studied. Data were obtained from standardized obstetrical appointments (clinical history, serum biomarkers, placental ultrasound) and hospital delivery records (pregnancy complications, delivery details and perinatal outcomes). Placental pathology was performed in all subjects using standard criteria. RESULTS In our cohort, 72% of women were Caucasian, 14% East Asian, 8% South Asian, 4% Afro-Caribbean and 3% Hispanic women. 81% of couples were concordant (same ethnic background) and 19% discordant (mixed ethnicities). South Asian women had the highest rate of small for gestational age (SGA) birth (customized birthweight <10th percentile) (24.2%), which was associated with the placental features of uteroplacental vascular insufficiency (placental weight <10th percentile with decidual vasculopathy, focal infarction, and/or syncytial knot formation) (p = 0.05). Placental efficiency varied significantly by ethnicity; Caucasian women had the highest efficiency (7.1 ± 1.2) and Afro-Caribbean women the lowest (6.5 ± 0.9) (p < 0.003). Afro-Caribbean women had the highest rate of marginal cord insertion. Placental efficiency, was higher in concordant vs. discordant couples (7.0 ± 1.2 vs. 6.8 ± 1.1; p < 0.05). Placental histopathology was not affected by parental ethnic discordance. DISCUSSION Maternal ethnicity influences placental efficiency and relationship between uteroplacental vascular insufficiency and SGA birth, but was not associated with other placental pathologies. Discordant parental ethnicity did not affect the development of placental pathologies or adverse pregnancy outcomes.