Effects of caesarean section on maternal health in low risk nulliparous women: a prospective matched cohort study in Shanghai, China

Abstract

Background: Rates of caesarean section are progressively increasing in many parts of the world. As a result of psychosocial factors there has been an increasing tendency for pregnant women without justifiable medical indications for caesarean section to ask for this procedure in China. A critical examination of this issue in relation to maternal outcomes is important. At present there are no clinical trials to help assess the risks and benefits of caesarean section in low risk women. To fill the gap left by trials, this indication-matched cohort study was carried out to examine prospectively the outcomes of caesarean section on women with no absolute obstetric indication compared with similar women who had vaginal delivery.

Methods: An indication-matched cohort study was undertaken to compare maternal outcomes following caesarean section with those undergoing vaginal delivery, in which the two groups were matched for non-absolute indications. 301 nulliparous women with caesarean section were matched successfully with 301 women who delivered vaginally in the Maternal and Children's Hospitals (MCHs) in Shanghai, China. Logistic regression model or binomial regression model was used to estimate the relative risk (RR) directly. Adjusted RRs were calculated adjusting for propensity score and medical indications.

Results: The incidence of total complications was 2.2 times higher in the caesarean section group during hospitalization post-partum, compared with the vaginal delivery group (RR = 2.2; 95% CI: 1.1-4.4). The risk of haemorrhage from the start of labour until 2 hours post-partum was significantly higher in the caesarean group (RR = 5.6; 95% CI: 1.2-26.9). The risk of chronic abdominal pain was significantly higher for the caesarean section group (RR = 3.6; 95% CI: 1.2-10.9) than for the vaginal delivery group within 12 months post-partum. The two groups had similar incidences of anaemia and complicating infections such as wound complications or urinary tract infection.

Conclusions: In nulliparous women who were at low risk, caesarean section was associated with a higher rate of post-partum morbidity. Those requesting the surgical procedure with no conventional medical indication, should be advised of the potential risks.

Figure 1

Group classification and matching. ^a Women with absolute medical indications for caesarean section were excluded in the study; ^b Women with relative indications in the caesarean section group were matched with those who delivered vaginally; ^c Women with no indications in the caesarean section group were matched with those who delivered vaginally.

Figure 2

Flow diagram of screening, matching and follow-up indicating losses from the original cohort of the study. ^a The preliminary screening was conducted in the antenatal clinics and re-screening in the maternity wards after birth; ^b Eligible women in the caesarean section group were matched with those who delivered vaginally (Figure 1) according to the matching criteria; ^c Post-partum investigations were made in the maternity wards, and follow-up of 1 month, 6 months and 12 months post-partum in the Maternity and Child Health Institutes affiliated to MCHs.