Objective: To evaluate the risk of severe acute maternal morbidity (SAMM) related to mode of delivery.
Design: Prospectively nationwide population based cohort study. Setting. All 98 maternity units in the Netherlands.
Population: All pregnant women in the Netherlands.
Methods: Cases were collected during a 2-year period. Incidence was assessed for all cases and for a subgroup of cases in which a direct relation between SAMM and mode of delivery was possible. In the latter group, all cases not clearly related to mode of delivery were excluded. Incidence of cesarean section (CS) compared to (attempted) vaginal delivery was calculated, and risk of SAMM after previous CS was assessed.
Main outcome measures: Incidence of SAMM by mode of delivery; odds ratios (OR).
Results: The incidence of SAMM possibly related to mode of delivery was 6.4/1,000 during elective CS compared to 3.9/1,000 during attempted vaginal delivery (OR 1.7: 95% CI 1.4-2.0). Women with a previous CS were at increased risk for SAMM in their present pregnancy (OR 3.0: 95% CI 2.7-3.3).
Conclusion: CS in a previous as well as present pregnancy increased the risk of SAMM. The risk remained increased after excluding those cases where SAMM was not clearly related to mode of delivery.