Large babies and unplanned Caesarean delivery

Objective: The relationship between birth weight ≥4000 g and unplanned Caesarean delivery was examined. Design: A retrospective cohort study. Setting: A district general hospital. Population: Two thousand three hundred and ninety-three women who delivered babies weighing ≥2500 g. Methods: The mode of delivery of babies who weighed ≥4000 g was compared with those who weighed between 2500 and 4000 g. Comparative analysis of data was followed by regression analysis of explanatory variables. The effect of increasing birth weight on unplanned Caesarean delivery was determined. Results: Women who had an unplanned Caesarean were delivered at an earlier gestation (OR=0.89, 95% CI 0.81-0.97; P=0.007), and were more likely to be primiparous (OR 5.4, 95% CI 4.1-7.1; P=0.0001). Further, women who had an unplanned Caesarean were more likely to have babies weighing ≥4000 g (OR=2.24, 95% CI 1.61-3.12; P=0.003). The odds of having an unplanned Caesarean were increased 16.9-fold with a previous Caesarean (95% CI 9.24-30.8; P=0.001). When a previous Caesarean was combined with a baby weighing ≥4000 g, the odds of having an unplanned Caesarean increased 37.8 times (95% CI 18.8-75.8), compared to a woman who previously had a normal vaginal birth and a baby weighing between 2500 and 4000 g. Conclusion: Birth weight ≥4000 g is associated with more than a two-fold increased risk of an unplanned Caesarean delivery. The risk increased further (37.8×) when a previous Caesarean delivery was combined with a birth weight ≥4000 g.