Date

May 2009

Document Type

Thesis

Degree Name

M.P.H.

Department

Dept. of Public Health and Preventive Medicine

Institution

Oregon Health & Science University

Abstract

Background The health consequences of smoking during pregnancy, both to the prospective mother and to the infant, have long been recognized. However, very little is known about why some women avoid detrimental behaviors and engage in beneficial ones, while others do not. It is encouraging to note that approximately 40-44% of women who smoke at the start of pregnancy quit smoking for the duration of the pregnancy. Unfortunately, more than half of these women return to smoking within 6 months postpartum. While trends in smoking prevalence during pregnancy are known, little is known about trends in quitting during pregnancy and staying quit, postpartum. This project aims to identify and differentiate between characteristics of those women who quit smoking during pregnancy and managed to stay quit, 2 years postpartum. Women who smoked during pregnancy and those who quit smoking during pregnancy will be compared to identify characteristics of women who quit smoking during pregnancy. In addition, we aim to identify characteristics of those women who stayed quit, 2 years postpartum compared to those women who relapsed into smoking, 2 years postpartum. Methods This study used data from the 2004 Oregon Pregnancy Risk Assessment Monitoring System (PRAMS) and its 2006 longitudinal follow-up, PRAMS-2. 1,968 women were surveyed with the 2004 Oregon PRAMS and 865 of these women responded to the 2-year follow-up survey in 2006 with a weighted response rate of 51.1%. In the PRAMS questionnaire, women were asked: “Have you smoked 100 cigarettes in the past 2 years? (A pack has 20 cigarettes.)” Only those who reported smoking at least 100 cigarettes in the past 2 years were included in this analysis. Smoking intensity was measured at three time points in PRAMS – 3 months before pregnancy (T1), last 3 months of pregnancy (T2) and 2-6 months postpartum (T3) with the question: “In the (time point), how many cigarettes did you smoke on an average day? (A pack has 20 cigarettes.)” PRAMS-2 measured smoking intensity at a fourth time point – 2 years postpartum (T4) – only to those who answered ‘Yes’ to the question: “Have you smoked 100 cigarettes in your entire life? (A pack has 20 cigarettes.)” Possible responses were None, Less than 1 cigarette, 1 to 5 cigarettes, 6 to 10 cigarettes, 11 to 20 cigarettes, 21 to 40 cigarettes, 41 cigarettes or more. The respondents were classified into the following categories: (i) Smoked during pregnancy, (ii) Quit smoking during pregnancy, (iii) Stayed quit 2 years postpartum, (iv) Relapsed into smoking, 2 years postpartum, and, (v) Persistent smokers – Women who smoked at all the 4 time points. Women who smoked during pregnancy were compared with women who quit smoking during pregnancy to identify characteristics of those women who quit smoking during pregnancy. Women who stayed quit 2 years postpartum were compared with women who relapsed into smoking 2 years postpartum to explore characteristics of women who stayed quit 2 years postpartum. Logistic regression was used to highlight characteristics of women who quit smoking during pregnancy and identify potential correlates of staying quit, 2 years postpartum. Hosmer & Lemeshow’s model building techniques were used to build a multivariable logistic regression model to determine the characteristics of women who quit smoking during pregnancy and of women who stayed quit, 2 years postpartum. All analyses used weighted data to account for the complex sampling design utilized by PRAMS and PRAMS-2. Results - Quit smoking during pregnancy In logistic regression analyses, marginally significant factors associated with quitting smoking during pregnancy were annual household income during pregnancy and WIC participation during pregnancy. Even though these results were only marginally significant in univariate analysis, the magnitude of the Odds Ratios warrants discussion of these results for public health implications. Annual household income during pregnancy: Women who had higher annual household incomes (>=185% FPL category) were more likely to quit smoking than those who had lower annual household incomes (0-184% FPL category) (Unadjusted OR 3.68; 95% CI 0.98, 13.79), (Adjusted OR 2.17; 95% CI 0.50, 9.42). WIC during pregnancy: Women who did not use WIC during pregnancy were more likely to quit smoking during pregnancy than women who used WIC (Unadjusted OR 2.84; 95% CI 0.87, 9.21), (Adjusted OR 1.08; 95% CI 0.29, 4.03). Results - Stayed quit, 2 years postpartum Significant factors associated with women staying quit, 2 years postpartum, were: Maternal Education: Women who had greater than a high school education were more likely to stay quit, 2 years postpartum, than women who had a high school education or less (Unadjusted OR 20.33; 95% CI 4, 103.52), (Adjusted OR 13.30; 95% CI 2.36, 74.87). Depressive Symptoms in 13-24 months after delivery: This was perhaps the most striking finding of this study. Women who reported depressive symptoms 13-24 months after delivery were more likely to stay quit than women who did not report any depressive symptoms in the past 12 months (Unadjusted OR: 6.73, 95% CI 1.33, 34.08), (Adjusted OR 11.27; 95% CI 1.83, 69.52). Maternal age: Women who were greater than or equal to 25 years old were more likely to stay quit than women who were less than 25 years old in univariate analysis (Unadjusted OR: 8.92, 95% CI 1.35, 59.03). This association did not remain statistically significant in multivariate analysis (Adjusted OR 3.92; 95% CI 0.27, 57). Discussion We were able to identify marginally significant associations between annual household income during pregnancy and use of WIC during pregnancy with women who quit smoking during pregnancy. Significant risk factors for staying quit, identified in this preliminary analysis, included maternal education, maternal age and postpartum depressive symptoms. Because of the limited sample size that was available (68 women who quit smoking during pregnancy compared to 85 women who smoked during pregnancy), this study only had adequate power to detect Odds Ratios of 4.0 or higher for quitting smoking during pregnancy and 5.0 or higher for staying quit, 2 years postpartum (24 women who stayed quit 2 year postpartum compared to 34 women who relapsed into smoking 2 years postpartum). Further research is warranted to re-examine some additional well-known risk factors such as stressful life events, social support and people in household who smoke in conjunction with staying quit. This research could be useful in highlighting characteristics of women who quit smoking during pregnancy and providing some exploratory insight into characteristics of women who managed to stay quit, 2 years postpartum in order to be able to account for those characteristics while implementing smoking cessation interventions and ensuring efficient distribution of limited resources.

Identifier

doi:10.6083/M4KK98RJ

School

School of Medicine

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