Of the 1,136,437 births included in the analysis, 34,575 (3.0%) were to mothers who reported smoking during pregnancy (). The mean maternal age was 28.9 years (standard deviation = 6.3 years, range = 12–57 years). The population of women giving birth was ethnically diverse. The single largest group (non-Hispanic white women) comprised only 28.1% of the total, and the majority of women were born outside the U.S. (52.8%). The percentage of foreign-born women increased from 51.1% in 1995 to 54.3% in 2005. For most women, this was at least their second pregnancy (55.6%) and prenatal care had been initiated in the first trimester (68.2%).
Univariate maternal characteristics and bivariate association with reported prenatal smoking, NYC, 1995–2005 (n=1,136,437)
The proportion of births to smoking mothers declined across the three time periods, from 4.5% in 1995–1998, to 2.9% in 1999–2002, to 1.7% in 2003–2005 (). Overall, we found minimal variation in the association between prenatal smoking and maternal age. As compared with women aged 20 to 29 years, those younger than 19 years of age were moderately more likely to smoke (OR=1.22, 95% CI 1.17, 1.27) and those aged 30 to 39 were minimally less likely to smoke (OR=0.97, 95% CI 0.95, 0.99). Women with fewer than nine years of education smoked 0.40 times less (95% CI 0.38, 0.42) than women who had nine to 12 years of school. The prevalence of smoking increased both with number of previous pregnancies and later initiation of prenatal care. Within NYC, we found regional differences in the prevalence of prenatal smoking. Women living in Staten Island smoked 2.93 times more (95% CI 2.81, 3.06) than women living in Queens.
African American (OR=2.75, 95% CI 2.69, 2.83) and Puerto Rican (OR=2.35, 95% CI 2.27, 2.42) women were substantially more likely to smoke as compared with non-Hispanic white women, and reported the highest prevalence of smoking among all ethnic groups. The concentration of smokers among U.S.-born women (82.3%) was reflected in the disparate prevalence of smoking across ethnic groups. No more than 1.0% of women in ethnic groups from either the non-Hispanic Caribbean, Mexico/Central/South America, Asia/Pacific Islands, or Africa smoked during pregnancy.
We found declines in the prevalence of prenatal smoking across the three time periods among all ethnic groups except other Hispanic (a category that includes Hispanic women from Spain, Cuba, or an unreported ancestral country; the majority are U.S.-born) and among all examined maternal subgroups except women with no prenatal care (). While tobacco use among all ethnic groups declined, the disparity between some ethnic groups widened. Compared with non-Hispanic white women, African American women had 2.46 increased odds (95% CI 2.36, 2.55) of smoking during 1995–1998, and 3.63 increased odds (95% CI 3.39, 3.88) of smoking during 2003–2005, despite an absolute reduction in smoking from 10.4% to 5.0% (). Puerto Rican women and those indicating other ethnicity both exhibited a pattern similar to African American women, with greater than 50.0% reductions in smoking prevalence juxtaposed to a widening disparity with smoking levels of non-Hispanic white women. The prevalence of smoking among Puerto Rican women dropped from 8.7% during 1995–1998 to 4.1% during 2003–2005, while the odds of smoking as compared with non-Hispanic white women increased from 2.01 (95% CI 1.92, 2.10) to 2.99 (95% CI 2.77, 3.24). Among women indicating other ethnicity, prevalence fell from 7.0% to 3.4%, but relative to non-Hispanic white women, the smoking OR increased from 1.60 in 1995–1998 (95% CI 1.36, 1.88) to 2.44 in 2003–2005 (95% CI 1.92, 3.10).
Maternal characteristics and bivariate association with reported prenatal smoking by time period, NYC, 1995–2005 (n=1,136,437)
Trends in prenatal smoking by maternal ethnicity, New York City, 1995–2005a
Overall, the odds of smoking in 2003–2005 were 0.44 (95% CI 0.43, 0.46) times less than in 1995–1998, adjusted for maternal age, ethnicity, nativity, parity, prenatal care initiation, education, and borough of residence (). Non-Hispanic white women experienced the largest adjusted drop in smoking prevalence (OR=0.34, 95% CI 0.32, 0.36) and other Hispanic women the smallest adjusted drop (OR=0.74, 95% CI 0.61, 0.91) across the three time periods.
Multivariate association between time period and reported prenatal smoking, New York City, 1995–2005 (n=1,136,437)