BMJ 1995;310:436-439 (18 February)

Papers

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

Ivan J Perry, lecturer in public health medicine,a D G Beevers, professor of medicine,b P H Whincup, senior lecturer in clinical epidemiology,a D Bareford, consultant haematologist b

a Department of Public Health, Royal Free Hospital School of Medicine, London NW3 2PF, b Departments of Medicine and Haematology, Dudley Road Hospital, Birmingham B18 7QH

Correspondence to: Dr Perry.

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, P<0.001) and multivariate analysis. The only other significant predictor of placental ratio in multivariate analysis was maternal body mass index, which was positively associated with placental ratio (r=0.1, P=0.01). Mean (SD) placental ratio was not significantly higher in women who developed gestational hypertension (20.4% (4.5%)) and pre-eclampsia (23.3% (7.3%)) than in normal women (19.8% (3.8%)). No evidence of a relation between placental ratio and first antenatal visit haemoglobin concentration or mean cell volume was detected, and placental ratio was not associated with change in mean cell volume during pregnancy or with third trimester serum ferritin concentration.
Conclusions: 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

  • 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


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