This analysis used smoking-related data from the first wave of the Growing Up in New Zealand cohort study, i.e. from the first data-collection point during the antenatal period in 2009–10. Of the 6,822 pregnant women recruited into the study, 1,946 reported that they smoked either before pregnancy (n=1,387 [20.4%]) or continued to smoke during pregnancy (n=559 [9.9%]). These figures were higher in younger women (aged ≤19 years; p<0.0001), women who were less educated (p<0.001) and Māori women (p<0.001). Similarly, being Māori (p<0.0001) and being less educated (p<0.0029) were associated with smoking during an unplanned compared to a planned pregnancy. During pregnancy, multiparous mothers were more likely to be smokers than primaparous mothers (11% vs 8.3%). Exposure to second-hand smoke was more common for younger women (OR 3.2; 95% CI, 1.6 to 6.4), Māori women (OR 1.9; 95% CI, 1.4 to 2.5), and women with unplanned pregnancies (OR 3.4; 95% CI, 12.0 to 14.8).
