An intervention aimed at helping pregnant women avoid exposure to secondhand tobacco smoke appeared to be successful at both meeting that goal and improving pregnancy outcomes in a sample of black women in a randomized, controlled trial conducted at six clinics in Washington, DC, in 2001–2004.1 Intervention participants had 50% lower odds than controls of reporting secondhand smoke exposure before delivery, as well as reduced odds of having a very low-birth-weight infant or a very preterm delivery. All trial participants reported that they did not smoke during pregnancy, and this report was corroborated for most by a test that detects a biomarker of tobacco exposure in saliva; results for this subgroup were similar to those for the overall sample.
The trial was part of a larger project designed to lower infant mortality levels among minority groups. Women attending the study clinics were eligible to participate if they belonged to an ethnic minority group; were at least 18 years old and no more than 28 weeks pregnant; lived in the District of Columbia; spoke English; and either smoked cigarettes, were exposed to secondhand smoke at home or in a car during a typical week, were depressed or experienced intimate partner violence. Telephone interviews at 22–26 weeks of gestation and again at 34–38 weeks tracked women’s behavioral risks; medical record review provided information about medical risks and pregnancy outcomes.
The analyses were based on the 691 black participants who said that they did not smoke but were exposed to secondhand smoke during pregnancy. This group was randomly assigned to receive either usual care (356 women) or the intervention (335), which taught women strategies to eliminate or reduce exposure to secondhand smoke in the home (e.g., negotiating with household members who smoked) and explained the potential risks of exposure to secondhand smoke. Saliva samples were tested for cotinine, a nicotine by-product, and analyses were repeated using data on the 520 women whose tests confirmed that they were nonsmokers.
Baseline characteristics of the intervention and comparison groups were similar. Women’s average age was 23–24, about one-quarter had less than a high school education, one-quarter were married or cohabiting, and close to four in 10 were employed. The majority of women were on Medicaid (76–80%) and had begun prenatal care early (58–61%). Roughly 10–20% reported substance use during pregnancy. Forty percent of each group were depressed, and 30–31% reported intimate partner violence.
At the third-trimester follow-up interview, 54% of women in the intervention group reported that they were regularly exposed to secondhand smoke—a significantly lower proportion than the 68% found in the comparison group. Findings were similar for the subgroup of women whose saliva tests confirmed that they were nonsmokers: Some 54% and 66%, respectively, reported secondhand smoke exposure. Results of logistic regression analysis supported the association: The odds of secondhand smoke exposure were reduced among intervention participants in both the overall sample (odds ratio, 0.5) and the subgroup (0.6). Increasing maternal age also was associated with reduced odds of exposure in the overall sample (0.96); in both samples, Medicaid recipients were more likely than others to experience regular exposure to secondhand smoke (1.7–2.0).
Bivariate comparisons of a variety of pregnancy outcomes revealed two differences between women in the intervention and comparison groups. The former were less likely than the latter to have a very low-birth-weight infant (one weighing less than 1,500 g) and to have a very preterm birth (-delivery before 34 weeks’ gestation)—0.4% vs. 3% and 1% vs. 6%, respectively. Again, the associations were confirmed in multivariate analysis: Intervention participants had substantially reduced odds of having a very low-birth-weight infant (odds ratio, 0.1) or a very preterm birth (0.2). In addition, those who had previously delivered preterm or who reported intimate partner violence at baseline had elevated odds of these outcomes. Among women confirmed as nonsmokers, participation in the intervention was associated with reduced odds of very preterm birth (0.1).
The researchers cite national data indicating that black women are less likely than whites to smoke during pregnancy. However, they caution that black women should not be assumed to have a low risk of exposure to tobacco smoke, because smoking prevalence is high among black men, and many black women live in overcrowded -households and cannot control the home environment. Therefore, while acknowledging the limitations of the study (including its use of a small, high-risk sample of women and the intervention’s reliance on specially trained providers), they emphasize that it was "the first, to our knowledge, to show that a -cognitive--behavioral intervention that is delivered during [prenatal care] can assist black mothers in reducing their risk for [-secondhand smoke exposure] and improving their pregnancy outcomes." Furthermore, the researchers comment, the reduction in the rates of very preterm birth are important "because the smallest and most preterm infants are…at the highest risk for death and significant morbidity."
—D. Hollander