Association Between Preconception Maternal Mental Health-Related Hospitalisation (MHrH) and Outcomes During Pregnancy: A Population-Based Cohort Study in the Northern Territory, Australia

Comprehensive studies investigating the link between maternal hospitalisation for mental health conditions prior to pregnancy and adverse outcomes in pregnancy are scarce in Australia. We aimed to fill this gap by using 18 years of administratively linked data to inform early interventions. We linked the perinatal data from the year 1999 to 2017 to the hospital hospitalisation data to create a cohort of pregnant women aged 15 to 44 years who gave birth in the Northern Territory (NT). We used the International Classification of Disease 10th revision (ICD-AM-10) codes to locate women with mental health-related hospitalisation (MHrH) (exposure of interest) and the perinatal data to access pregnancy outcomes. We used the modified Poisson regression with robust standard error to estimate the risk of pregnancy outcomes associated with maternal MHrH in the 5 years prior to pregnancy. We calculated the adjusted population attributable fraction (aPAF) for valid associations. We used the E-value to assess the effect of potential confounding bias. Out of 69,890 pregnancies, similar to 67,518 were eligible and included in the analysis. We found a significant variation in the incidence of substance use and complications between Aboriginal and non-Aboriginal women and women with and without MHrH in the 5 years prior to pregnancy. After adjusting, 5 years of preconception hospitalisation for substance misuse was associated with a 31% (95%CI, 1.05, 1.63) increased risk of Intrauterine Growth Restriction (IUGR), a 60% (CI, 1.37, 1.86) increased risk of smoking and a 2.21 (CI, 1.98, 2.47) times increased risk of drinking during pregnancy in Aboriginal women; and a 17% increased risk of drinking (CI, 1.11, 1.23) in pregnancy in non-Aboriginal women. A significant proportion of smoking (aPAF = 14.7 to 37.4%), alcohol consumption (aPAF = 46.0 to 66.7%), and IUGR (aPAF = 23.6 to 38.5%) are attributed to maternal MHrH 5 years prior to pregnancy. Our findings are a 'wake-up' call for strengthening preconception care to reduce adverse outcomes of maternal MHrH prior to pregnancy.