Outcome of preterm infants (<30 weeks) born to mothers who smoked: propensity score matching study

Maternal smoking has been associated with adverse neonatal outcomes; specifically, outcomes of preterm-born after maternal smoking have not been studied.

To compare the short-term hospital outcomes of preterm infants born to mothers who 'ever smoked' with matched preterm infants born to mothers who 'never smoked'.

This was a matched retrospective cohort study including all preterm infants <30 weeks between March 2019 and March 2023. Matching was performed, creating propensity scores with 'Mother ever smoked versus Mother never smoked' as dependent outcomes with birth gestational age, baby gender and Apgar score at 1 min as covariates. The standardised mean difference (SMD) was used to assess any potential imbalance. Appropriate statistical tests were applied.

We had a total of 179 preterm infants born <30 weeks. After excluding 26 deaths, we had a total of 153 infants available for analysis before matching. After matching, we had 46 infants in each group (table 1). There was no imbalance between the baseline demographic and clinical factors, with all SMDs ≤0.1, except for the Apgar score at 10 min. Infants in the smoking group were significantly less likely to need surfactant (OR: 0.33) and were highly likely to be discharged on home oxygen (OR: 2.7). There was no difference in death rates between the two groups (16% in the non-smoking group vs 12% in the smoking group).

In this propensity score matching study, infants whose mothers ever smoked were more likely to be discharged on home oxygen.