Systematic Review and Meta-Analyses of Perinatal Death and Maternal Exposure to Tobacco Smoke During Pregnancy

We conducted a systematic review and 3-part meta-analysis to characterize the relationship between smoking and perinatal death, defined as the combination of stillbirth and neonatal death. The PubMed database was searched (1956-August 31, 2011) with keywords, and manual reference searches of included articles and Surgeon Generals' reports were conducted. The full texts of 1,713 articles were reviewed, and 142 articles that examined the associations between active or passive smoking and perinatal death were included in the meta-analyses. Data were abstracted by 2 reviewers. Any active maternal smoking was associated with increased risks of stillbirth (summary relative risk (sRR) = 1.46, 95% confidence interval (CI): 1.38, 1.54 (n = 57 studies)), neonatal death (sRR = 1.22, 95% CI: 1.14, 1.30 (n = 28)), and perinatal death (sRR = 1.33, 95% CI: 1.25, 1.41 (n = 46)). The risks of stillbirth, neonatal death, and perinatal death increased with the amount smoked by the mother. Biases in study publication, design, and analysis were present but did not significantly affect the results. These findings strengthen the evidence that women should not smoke while pregnant, and all women of reproductive age should be warned that smoking increases the risks of stillbirth, neonatal death, and perinatal death.