Mental Disorders Among Mothers of Children Born Preterm: A Population-Based Cohort Study in Canada.

Background: Our aim was to examine the association between preterm delivery and incident maternal mental disorders using a population-based cohort of mothers in Canada.
Methods: Retrospective matched cohort study using Manitoba Centre for Health Policy (MCHP) administrative data in Manitoba. Mothers who delivered preterm babies (<37 weeks gestational age) between 1998 and 2013 were matched 1:5 to mothers of term babies using socio-demographic variables. Primary outcome was any incident mental disorder within 5 years of delivery defined as any of (a) mood and anxiety disorders, (b) psychotic disorders, (c) substance use disorders, and (d) suicide or suicide attempts. Multivariable Poisson regression model was used to estimate the 5-year adjusted incidence rate ratios (IRRs).
Results: Mothers of preterm children ( N    =   5,361) had similar incidence rates of any mental disorder (17.4% vs. 16.6%, IRR   =   0.99, 95% CI, 0.91 to 1.07) compared to mothers of term children ( N    =   24,932). Mothers of term children had a higher rate of any mental disorder in the first year while mothers of preterm children had higher rates from 2 to 5 years. Being the mother of a child born <28 week (IRR   =   1.5, 95% CI, 1.14 to 2.04), but not 28-33 weeks (IRR   =   1.03, 95% CI, 0.86 to 1.19) or 34-36 weeks (IRR   =   0.96, 95% CI, 0.88 to 1.05), was associated with any mental disorder.
Interpretation: Mothers of preterm and term children had similar rates of incident mental disorders within 5-years post-delivery. Extreme prematurity was a risk factor for any mental disorder. Targeted screening and support of this latter group may be beneficial.