Predictors of ratio of placental weight to fetal weight in multiethnic community

Abstract

Objective: To determine whether placental ratio is influenced by maternal ethnic origin, obesity, hypertension, and haematological indices of iron deficiency anaemia. Design: Observational study. Setting: District general hospital in Birmingham. Subjects: 692 healthy nulliparous pregnant women, of whom 367 were European, 213 Asian, 99 Afro-Caribbean, and 13 of other or undocumented ethnic origin. Main outcome measures: Placental ratio and maternal body mass index, blood pressure, and haematological indices. Results: Though birth weight and placental weight were lower in Asian women than in other groups, mean placental ratio was similar in Asian (19.5% (SD 3.3%)), European (20.0% (4.0%)), and Afro-Caribbean women (20.4% (5.3%)). Gestational age at birth was the main predictor of placental ratio in the univariate analysis (r= -0.34, PConclusions: These data do not support the proposed association between poor maternal nutrition and increased placental ratio. The association between high placental ratio and adult hypertension may be confounded by genetic and environmental factors associated with maternal obesity (and possibly maternal hypertension). Key messages Poor maternal nutrition has been suggested as a determinant of placental ratio, and an association with haematological indices of iron deficiency anaemia has been described In this study of European, Asian, and Afro-Caribbean pregnant women placental ratio was increased in the offspring of obese women Placental ratio was not significantly associated with first antenatal visit haemoglobin concentrations or mean cell volume, change in mean cell volume between the first antenatal visit and the third trimester, or third trimester serum ferritin concentration These findings do not support the hypothesis that raised placental ratio is a marker for poor maternal nutrition