Birth weight and ponderal index in pre-eclampsia: a comparative study

Abstract

Summary objective: To evaluate the effects of early-onset and late-onset pre-eclampsia on fetal growth.

Design: Longitudinal prospective analytical survey

Setting: Obstetrics unit of Department of Obstetrics and Gynaecology in Korle Bu Teaching Hospital.

Subjects and methods: 11,784 nulliparous women carrying singleton pregnancy were prospectively followed up based on a schedule of antenatal care from 14-16 weeks gestation till delivery. Exclusion criteria included obesity (BMI>30.0), underweight (BMI<18.5), chronic hypertension, diabetes mellitus, chronic renal disease, connective tissue diseases, hyperthyroidism, hypothyroidism, cardiac disease, HIV/AIDS, anaemia (Hb<10.0 g/dL), malaria during the index pregnancy, alcohol abuse and cigarette smoking. The selected women were observed for onset of pre-eclampsia, timing of delivery, and baby's birth weight and crown-heel length for each baby were entered into a register. The ponderal index of each baby at birth was also computed.

Results: The incidence of pre-eclampsia in the 11,784 women was 7.03%. The babies delivered by mothers who had early-onset (<37 weeks gestation) pre-elampsia, were of significantly lower birth weights (p=0.003 to p=0.02) and ponderal indices (p=0.002 to p=0.02) at all gestational ages of delivery compared with babies of mothers who did not have pre-eclampsia. However, in late-onset (>/=37 weeks) pre-eclampsia, the birth weights and ponderal indice at all gestational ages were comparable to non-pre-eclamptics.

Conclusion: These results support the hypothesis that pre-eclampsia is an aetiologically heterogenous disorder that occurs in at least two subsets: a late-onset pre-eclampsia with normal fetal growth denoting normal placental function and an early-onset type with fetal growth restriction implying placental dysfunction.