Parental smoking during pregnancy: findings from the Growing Up in New Zealand cohort.

AIMS To investigate patterns of exposure to tobacco smoke in pregnancy among a representative sample of New Zealand women. METHODS Analyses of smoking-related data from the first wave of the Growing Up in New Zealand cohort study, ie from the first data-collection point during the antenatal period in 2009-10. RESULTS Twenty percent of mothers reporting smoking before pregnancy and 9.9% of mothers continued during pregnancy. These figures were higher in younger women (p<.0001), women with lower educational achievement (p<.001) and Māori women (p<.001). Similarly, being Māori (p<.0001) and having a lower education achievement (p<.0029) were associated with smoking during an unplanned compared to a planned pregnancy. Multiparous mothers were more likely to be smokers than primaparous mothers (11%: 95% Confidence Interval [CI] 10.0-12.1 vs 8.3%: 95% CI 7.2-9.4). Second-hand smoke exposure was more common for younger women (Odds Ratio [OR] 3.2: 95% CI 1.6-6.4), Māori women (OR 1.9: 95% CI 1.4-2.5), and women with unplanned pregnancies (OR 3.4 95% CI 12.0-14.8). CONCLUSIONS There are differences in a range of contextual and behavioural factors related to smoking before and during pregnancy. Low educational achievement, being young, Māori and multiparous were all associated with smoking during pregnancy. A better understanding of why these differences exist is needed in order to find appropriate interventions to support women in becoming smoke-free.