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

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

Longitudinal prospective analytical survey

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

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.

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.

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.