Self-harm risk in pregnancy: recurrent-event survival analysis using UK primary care data.

Background: Perinatal self-harm is of concern but poorly understood.
Aims: To determine if women's risk of self-harm changes in pregnancy and the first postpartum year, and if risk varies by mental illness, age and birth outcome.
Method: This was a retrospective cohort study of 2 666 088 women aged 15-45 years from the 1 January 1990 to 31 December 2017 linked to 1 102 040 pregnancies and their outcomes, utilising the Clinical Practice Research Datalink and Pregnancy Register. We identified self-harm events and mental illness (depression/anxiety/addiction/affective/non-affective psychosis/eating/personality disorders) from clinical records and grouped women's age into 5-year bands. They calculated the rate of self-harm during discrete non-perinatal, pregnant and postpartum periods. We used a gap-time, stratified Cox model to manage multiple self-harm events, and calculated the unadjusted and adjusted hazard ratios (adjHR) of self-harm associated with pregnancy and the postpartum compared with non-perinatal periods. Pre-planned interactions tested if risk varied by mental illness, age and birth outcome.
Results: The analysis included 57 791 self-harm events and 14 712 319 person-years of follow-up. The risk of self-harm shrank in pregnancy (2.07 v. 4.01 events/1000 person-years, adjHR = 0.53, 95% CI 0.49-0.58) for all women except for 15- to 19-year-olds (adjHR = 0.95, 95% CI 0.84-1.07) and the risk reduced most for women with mental illness (adjHR = 0.40, 95% CI 0.36-0.44). Postpartum, self-harm risk peaked at 6-12 months (adjHR = 1.08, 95% CI 1.02-1.15), at-risk groups included young women and women with a pregnancy loss or termination.
Conclusions: Maternity and perinatal mental health services are valuable. Family planning services might have psychological benefit, particularly for young women.