Congenital malformations are associated with secondhand smoke among nonsmoking women: A meta-analysis

Exposure to second-hand smoke is common in many countries but the magnitude of the problem worldwide is poorly described. We aimed to estimate the worldwide exposure to second-hand smoke and its burden of disease in children and adult non-smokers in 2004. The burden of disease from second-hand smoke was estimated as deaths and disability-adjusted life-years (DALYs) for children and adult non-smokers. The calculations were based on disease-specific relative risk estimates and area-specific estimates of the proportion of people exposed to second-hand smoke, by comparative risk assessment methods, with data from 192 countries during 2004. Worldwide, 40% of children, 33% of male non-smokers, and 35% of female non-smokers were exposed to second-hand smoke in 2004. This exposure was estimated to have caused 379,000 deaths from ischaemic heart disease, 165,000 from lower respiratory infections, 36,900 from asthma, and 21,400 from lung cancer. 603,000 deaths were attributable to second-hand smoke in 2004, which was about 1·0% of worldwide mortality. 47% of deaths from second-hand smoke occurred in women, 28% in children, and 26% in men. DALYs lost because of exposure to second-hand smoke amounted to 10·9 million, which was about 0·7% of total worldwide burden of diseases in DALYs in 2004. 61% of DALYs were in children. The largest disease burdens were from lower respiratory infections in children younger than 5 years (5,939,000), ischaemic heart disease in adults (2,836,000), and asthma in adults (1,246,000) and children (651,000). These estimates of worldwide burden of disease attributable to second-hand smoke suggest that substantial health gains could be made by extending effective public health and clinical interventions to reduce passive smoking worldwide. Swedish National Board of Health and Welfare and Bloomberg Philanthropies. Copyright © 2011 Elsevier Ltd. All rights reserved.

To determine the risk of adverse fetal outcomes of secondhand smoke exposure in nonsmoking pregnant women. This was a systematic review and meta-analysis in accordance with Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. We searched Medline and Embase (to March 2009) and reference lists for eligible studies; no language restrictions were imposed. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were estimated by using random-effect models. Our search was for epidemiologic studies of maternal exposure to secondhand smoke during pregnancy in nonsmoking pregnant women. The main outcome measures were spontaneous abortion, perinatal and neonatal death, stillbirth, and congenital malformations. We identified 19 studies that assessed the effects of secondhand smoke exposure in nonsmoking pregnant women. We found no evidence of a statistically significant effect of secondhand smoke exposure on the risk of spontaneous abortion (OR: 1.17 [95% CI: 0.88-1.54]; 6 studies). However, secondhand smoke exposure significantly increased the risk of stillbirth (OR: 1.23 [95% CI: 1.09-1.38]; 4 studies) and congenital malformation (OR: 1.13 [95% CI: 1.01-1.26]; 7 studies), although none of the associations with specific congenital abnormalities were individually significant. Secondhand smoke exposure had no significant effect on perinatal or neonatal death. Pregnant women who are exposed to secondhand smoke are estimated to be 23% more likely to experience stillbirth and 13% more likely give birth to a child with a congenital malformation. Because the timing and mechanism of this effect is not clear, it is important to prevent secondhand smoke exposure in women before and during pregnancy.

While active maternal tobacco smoking has well established adverse perinatal outcomes, the effects of passive maternal smoking, also called environmental tobacco exposure (ETS), are less well studied and less consistent. To determine to the effect of ETS on perinatal outcomes. Medline, EMBASE and reference lists were searched. Studies comparing ETS-exposed pregnant women with those unexposed which adequately addressed active maternal smoking. Two reviewers independently assessed titles, abstracts, full studies, extracted data and assessed quality. Dichotomous data were pooled using odds ratios (OR) and continuous data with weighted mean differences (WMD) using a random effects model. Seventy-six articles were included with a total of 48,439 ETS-exposed women and 90,918 unexposed women. ETS-exposed infants weighed less [WMD -60 g, 95% confidence interval (CI) -80 to -39 g], with a trend towards increased low birthweight (LBW, < 2,500 g; RR 1.16; 95% CI 0.99-1.36), although the duration of gestation and preterm delivery were similar (WMD 0.02 weeks, 95% CI -0.09 to 0.12 weeks and RR 1.07; 95% CI 0.93-1.22). ETS-exposed infants had longer infant lengths (1.75 cm; 95% CI 1.37-2.12 cm), increased risks of congenital anomalies (OR 1.17; 95% CI 1.03-1.34) and a trend towards smaller head circumferences (-0.11 cm; 95% CI -0.22 to 0.01 cm). ETS-exposed women have increased risks of infants with lower birthweight, congenital anomalies, longer lengths, and trends towards smaller head circumferences and LBW.