This study assessed the extent to which women's preconception binge drinking, tobacco use and cannabis use, reported prospectively in adolescence and young adulthood, predicted use of these substances during pregnancy and at 1 year postpartum.

Data were pooled from two intergenerational cohort studies: the Australian Temperament Project Generation 3 Study (395 mothers, 691 pregnancies) and the Victorian Intergenerational Health Cohort Study (398 mothers, 609 pregnancies). Alcohol, tobacco and cannabis use were assessed in adolescence (13–18 years), young adulthood (19–29 years) and at ages 29–35 years for those transitioning to parenthood. Exposures were weekly or more frequent preconception binge drinking (5 + drinks in one session), tobacco use and cannabis use. Outcomes were any alcohol, tobacco and cannabis use prior to awareness of the pregnancy, after awareness of pregnancy (up to and including the third trimester pregnancy) and at 1 year postpartum.

Frequent preconception binge drinking, tobacco use and cannabis use across both adolescence and young adulthood were strong predictors of continued use post-conception, before and after awareness of the pregnancy and at 1 year postpartum. Substance use limited to young adulthood also predicted continued use post-conception.

Persistent alcohol, tobacco use and cannabis use that starts in adolescence has a strong continuity into parenthood. Reducing substance use in the perinatal period requires action well before pregnancy, commencing in adolescence and continuing into the years before conception and throughout the perinatal period.

Rates of common mental health problems (depression/anxiety) rise sharply in adolescence and peak in young adulthood, often coinciding with the transition to parenthood. Little is known regarding the persistence of common mental health problems from adolescence to the perinatal period in both mothers and fathers.

A total of 393 mothers (686 pregnancies) and 257 fathers (357 pregnancies) from the intergenerational Australian Temperament Project Generation 3 Study completed self-report assessments of depression and anxiety in adolescence (ages 13–14, 15–16, 17–18 years) and young adulthood (ages 19–20, 23–24, 27–28 years). The Edinburgh Postnatal Depression Scale was used to assess depressive symptoms at 32 weeks pregnancy and 12 months postpartum in mothers, and at 12 months postpartum in fathers.

Most pregnancies (81%) in which mothers reported perinatal depression were preceded by a history of mental health problems in adolescence or young adulthood. Similarly, most pregnancies (83%) in which fathers reported postnatal depression were preceded by a preconception history of mental health problems. After adjustment for potential confounders, the odds of self-reporting perinatal depression in both women and men were consistently higher in those with a history of persistent mental health problems across adolescence and young adulthood than those without (ORwomen 5.7, 95% CI 2.9–10.9; ORmen 5.5, 95% CI 1.03–29.70).

Perinatal depression, for the majority of parents, is a continuation of mental health problems with onsets well before pregnancy. Strategies to promote good perinatal mental health should start before parenthood and include both men and women.

Maternal mental health during pregnancy and postpartum predicts later emotional and behavioural problems in children. Even though most perinatal mental health problems begin before pregnancy, the consequences of preconception maternal mental health for children's early emotional development have not been prospectively studied.

We used data from two prospective Australian intergenerational cohorts, with 756 women assessed repeatedly for mental health problems before pregnancy between age 13 and 29 years, and during pregnancy and at 1 year postpartum for 1231 subsequent pregnancies. Offspring infant emotional reactivity, an early indicator of differential sensitivity denoting increased risk of emotional problems under adversity, was assessed at 1 year postpartum.

Thirty-seven percent of infants born to mothers with persistent preconception mental health problems were categorised as high in emotional reactivity, compared to 23% born to mothers without preconception history (adjusted OR 2.1, 95% CI 1.4–3.1). Ante- and postnatal maternal depressive symptoms were similarly associated with infant emotional reactivity, but these perinatal associations reduced somewhat after adjustment for prior exposure. Causal mediation analysis further showed that 88% of the preconception risk was a direct effect, not mediated by perinatal exposure.

Maternal preconception mental health problems predict infant emotional reactivity, independently of maternal perinatal mental health; while associations between perinatal depressive symptoms and infant reactivity are partially explained by prior exposure. Findings suggest that processes shaping early vulnerability for later mental disorders arise well before conception. There is an emerging case for expanding developmental theories and trialling preventive interventions in the years before pregnancy.