Impact of preeclampsia and gestational hypertension on birth weight by gestational age.

The predominant etiologic theory of preeclampsia is that reduced uteroplacental perfusion is the unique pathogenic process in the development of preeclampsia. Decreased uteroplacental blood flow would result in lower birth weights. To date, no study has assessed the effect of preeclampsia on birth weight by gestational age. Thus, the authors conducted a retrospective cohort study based on 97,270 pregnancies that resulted in delivery between 1991 and 1996 at 35 hospitals in northern and central Alberta, Canada. Differences in mean birth weight between women with preeclampsia and normotensive women ranged from -547.5 g to 239.5 g for gestational age categories ranging from < or = 32 weeks to > or = 2 weeks. The birth weights were statistically significantly lower among mothers with preeclampsia who delivered at < or = 37 weeks, with an average difference of -352.5 g. However, the birth weights were not lower among preeclamptic mothers who delivered after 37 weeks (average difference of 49.0 g). In Alberta, 61.2% of preeclamptic patients gave birth after 37 weeks of gestation. The authors conclude that babies born to mothers with preeclampsia at term have fetal growth similar to that of babies born to normotensive mothers. This finding does not endorse the currently held theory that reduced uteroplacental perfusion is the unique pathophysiologic process in preeclampsia.