The association between caesarean and postnatal psychological distress: Effect modification by mental health history

Abstract

Background: The association between mode of delivery and postnatal depression is uncertain. Mental health history may modify the association. Objectives: The objective of this study was to determine whether the association between caesarean and postnatal psychological distress (PPD) differs according to long-standing depression/anxiety. Methods: Analysis of the UK-based Millennium Cohort Study of women who gave birth 2000–2002 was carried out. The outcomes were PPD at 9 months by Rutter Malaise Inventory and actively treated physician-diagnosed depression/severe anxiety at 3 years. The exposure was mode of delivery. Adjusted relative risks were estimated using Poisson regression. Effect modification according to long-standing depression/anxiety was investigated multiplicatively and additively. Results: We included 15,936 women, of whom 2346 (13.4%, weighted) reported PPD. Women with long-standing depression/anxiety were at 34% lower risk of PPD following elective caesarean, compared with vaginal birth: relative risk (RR) 4.36 (95% confidence interval [CI] 3.76, 5.05), RR 3.25 (95% CI 2.23, 4.75) and RR 4.92 (95% CI 3.67, 6.59) for vaginal, elective and emergency caesarean births, respectively, with relative excess risk due to interaction (RERI) −1.28 (95% CI −2.73, 0.16), ratio of RRs 0.66 (95% CI 0.42, 1.05). Women with long-standing depression/anxiety were at greatest risk of later treatment following emergency caesarean, with RR 4.95 (95% CI 3.86, 6.34), RR 4.09 (95% CI 2.51, 6.65) and RR 6.74 (95% CI 4.87, 9.32), for vaginal, elective and emergency caesarean births, respectively; RERI 1.79 (95% CI −0.13, 3.71), ratio of RRs 1.36 (95% CI 0.94, 1.99); all RRs with reference to vaginal birth in the absence of long-standing depression/anxiety. There was no evidence of a similar association between emergency caesarean and PPD nor elective caesarean and later treatment. Conclusions: Women with long-standing depression or anxiety who had elective caesarean had a lower risk of postnatal distress. When this group had emergency caesarean, there was greater risk of actively treated depression/anxiety at 3 years. These associations were not observed in women without long-standing depression/anxiety.