Perinatal smoking in mothers and fathers: Longitudinal associations with infant birth outcomes.

Background: Parental smoking in pregnancy is an established risk for poorer infant health outcomes, yet knowledge on the impacts of smoking in the preconception and periconception periods is limited. Objective(s): This study examined the association between parental smoking at preconception, periconception and across pregnancy with infant birth outcomes.Study Design: Pregnant women and partners from the longitudinal Triple B Pregnancy Cohort Study (1,620 mothers; 820 fathers) were assessed across the perinatal period, and infants were assessed at birth. Associations were examined between maternal and paternal smoking at preconception (3 months pre-pregnancy), periconception (conception to pregnancy awareness), and during pregnancy (trimesters one, two and three), with hospital recorded infant birth statistics (low birth weight, prematurity, small head circumference, small-for-gestational age (SGA), and neonatal intensive care unit (NICU) admission).Results: Smoking was reported by 20% of mothers prior to conception, reducing to 10% post-pregnancy awareness. The frequency of partner smoking was stable across preconception and pregnancy (24%). Maternal preconception and periconception smoking were both associated with higher odds of infant admission to NICU (aOR = 1·74; aOR = 1·80, respectively). Periconception smoking was also associated with higher odds of prematurity (aOR = 2·05). Smoking in pregnancy was associated with higher odds of infant low birth weight (aOR = 2·77 to 3·53), prematurity (aOR = 2·79 to 3·78), SGA (aOR = 2.52 to 2·76), and admission to NICU (aOR = 2·21 to 2·40). Limited evidence was found for associations between maternal smoking and small head circumference. There was also limited evidence that perinatal smoking in fathers was associated with adverse infant outcomes, however, our sample of fathers comprised fewer daily smokers which may have impacted power to detect effects. Conclusion: Findings underscore the importance of earlier smoking cessation support for parents prior to, and during the early weeks of pregnancy, to reduce the harmful impacts of smoking on families.