Risk of complications in a second pregnancy following caesarean section in the first pregnancy: a population-based study.

OBJECTIVE

To estimate the risks of maternal and perinatal morbidity and mortality in a second pregnancy, attributable to caesarean section in a first pregnancy.

DESIGN AND SETTING

Cross-sectional analytic study of hospital births in New South Wales, based on linked population databases.

PARTICIPANTS

136 101 women with one previous birth who gave birth to a singleton infant in NSW in 1998-2002.

MAIN OUTCOME MEASURES

Crude and adjusted odds ratios (aOR) and 95% confidence intervals (95% CI) for maternal and perinatal morbidity and mortality.

RESULTS

19% of mothers had a caesarean section in their first pregnancy. Compared with mothers who had had primary vaginal births, mothers who had had primary caesarean section and underwent labour in the second birth were at increased risk of uterine rupture (aOR, 12.3; 95% CI, 5.0-30.1; P < 0.0001), hysterectomy (3.5; 1.5-8.4; P < 0.01), postpartum haemorrhage (PPH) following vaginal delivery (1.6; 1.4-1.7; P < 0.0001), manual removal of placenta (1.3; 1.1-1.6; P < 0.01), infection (6.2; 4.7-8.2; P < 0.0001) and intensive care unit (ICU) admission (3.1; 2.1-4.7; P < 0.0001); among mothers who did not undergo labour (ie, had an elective caesarean section), there was a lower risk of PPH (0.6; 0.5-0.7; P < 0.0001) and ICU admission (0.4; 0.3-0.5; P < 0.0001). For infants there was increased risk of preterm delivery (1.2; 1.1-1.3; P < 0.0001) and neonatal intensive care unit admission following labour (1.6; 1.4-1.9; P < 0.0001) in the birth after primary caesarean section. The occurrence of stillbirth was not modified by labour.

CONCLUSIONS

Caesarean section in a first pregnancy confers additional risks on the second pregnancy, primarily associated with labour. These should be considered at the time caesarean section in the first pregnancy is being considered, particularly for elective caesarean section for non-medical reasons.