Type of Labour in the First Pregnancy and Cumulative Perinatal Morbidity.

OBJECTIVE: To estimate cumulative perinatal morbidity among infants delivered at term, according to the type of labour in the first pregnancy, when the first pregnancy was low risk.

METHODS: In a 26-year population-based cohort study (1988-2013) using the Nova Scotia Atlee Perinatal Database, we identified the type of labour in successive pregnancies in low-risk, nulliparous women at term in their first pregnancy (who had at least one subsequent pregnancy), and also identified perinatal outcomes in subsequent deliveries according to the type of labour in the first pregnancy.

RESULTS: A total of 37 756 pregnancies satisfied inclusion and exclusion criteria; of these, 1382 (3.7%) had a Caesarean section without labour in the first pregnancy. Rates of most adverse perinatal outcomes were low (≤ 1%). The risks for stillbirth were low in subsequent deliveries, including those that followed CS without labour in the first pregnancy, and the risks for the overall severe perinatal morbidity outcome were less than 10% for all subsequent deliveries.

CONCLUSION: The absolute risks for severe perinatal morbidity outcomes in a population of low-risk women (with up to four additional pregnancies) were small, regardless of type of labour in the first pregnancy. This finding provides important information on perinatal outcomes in subsequent pregnancies when considering type of labour in the first pregnancy.