Smoking during pregnancy in an Irish obstetric Population: Prevalence, maternal and ethnic factors

Maternal cigarette smoking during pregnancy is associated with adverse health outcomes for the mother and her fetus in utero. A high prevalence of smoking during pregnancy is reported within an Irish obstetric population. However, there are no recent Irish data regarding change in smoking rates over time, or factors associated with declining smoking prevalence. Therefore, the objectives of this study were: 1. To investigate smoking patterns in pregnancy among an Irish obstetric population, 2. To identify trends over time, and 3. To evaluate associated demographic factors.

The data for this study were obtained from EuroKing, a computerised obstetric database, to which data had been entered prospectively during the 8-year period between January 2015 and December 2022 at Galway University Hospital, Ireland. A total of 22,673 deliveries were recorded during this time period. Complete information regarding the mother's smoking history was available for 19,247 women at the time of antenatal booking, and again at delivery. Statistical analyses was performed using GraphPad Prism (version 10.1.2). Chi-square test for proportions and trend were used to assess differences between groups.

Rates of smoking during pregnancy declined over the duration of the study. The percentage of mothers who smoked during pregnancy declined from 8.3 % in 2015 to 6.0 % in 2022 (P = 0.007). The greatest reduction in smoking was observed among those aged 21 to 30 years, from 15.3 % in 2015 to 10.1 % in 2022 (P < 0.001). There was no significant decline in smoking within the other age groups. There was an overall reduction in the rate of smoking from the time of antenatal booking to delivery of 31.9 %. Increasing maternal age was associated with lower rates of smoking (P < 0.001). Increasing parity was associated with higher rates of smoking (P < 0.001). Smoking rates were highest in the White Irish Traveller ethnic group, at 40.3 % across the 8-year study period. Breastfeeding rates were lower in smokers versus non-smokers (P < 0.001).

This study indicates that the rate of maternal smoking during pregnancy in Ireland is approximately 6%, which is less than previously reported. A significant proportion of women who smoked at the time of antenatal booking have ceased smoking by the time of delivery. Overall there was a decline in maternal smoking over the duration of the study. However, high rates of smoking were associated with certain sociodemographic characteristics, including younger maternal age, increasing parity and White Irish Traveller background.