Cigarette smoking during pregnancy and preeclampsia risk: a systematic review and meta-analysis of prospective studies

Abstract

Although evidence from epidemiological studies evaluating the association between cigarette smoking during pregnancy and preeclampsia risk has been systematically reviewed, the findings have been out of date. To further clarify the relationship, we conducted this comprehensive meta-analysis of prospective studies. We searched PubMed and Web of Science up to August 2015 to identify prospective studies that evaluated the association between cigarette smoking during pregnancy and preeclampsia risk. Random-effects models were used to estimate summarized relative risk (RR) and 95% confidence intervals (CIs). Seventeen prospective studies involving 62,089 preeclampsia patients from a total of approximately 1.8 million subjects were included. Overall, there was a significant negative association between smoking during pregnancy and incidence of preeclampsia (RR = 0.67, 95% CI: 0.60-0.75), with significant heterogeneity (I2 = 91.7%). Such an inverse association was also detected in strata of subgroup analyses according to study location, study sample size, parity of populations, singleton pregnancy, and adjustment for potential confounders including maternal age, diabetes mellitus, chronic hypertension, body mass index, and gender of infant. In summary, this meta-analysis suggests that smoking during pregnancy is inversely associated with incidence of preeclampsia. Further large scale multi-center prospective studies are warranted to validate our findings.

Keywords: cigarette smoking; meta-analysis; preeclampsia; risk factor.

Figure 1. Flow-chart of study selection

Figure 2. Forest plots (random effect model) of meta-analysis on the relationship between cigarette smoking during pregnancy and incidence of preeclampsia

Squares indicate study-specific risk estimates (size of the square reflects the study-specific statistical weight); horizontal lines indicate 95% CIs; diamond indicates the summary relative risk with its 95% CI. RR: relative risk.

Figure 3. Funnel plot corresponding to the random-effects meta-analysis of the relationship between cigarette smoking during pregnancy and preeclampsia risk

Figure 4. Sensitivity plot corresponding to the relationship between cigarette smoking during pregnancy and preeclampsia risk

Figure 5. Galbraith plot corresponding to the random-effects meta-analysis of the relationship between cigarette smoking during pregnancy and preeclampsia risk