The association between maternal smoking and hyperemesis gravidarum: a meta-analysis.

BACKGROUND

The majority of studies have not found hyperemesis to be a protective and some others have not. To date, no meta-analysis has quantitatively assessed the association between smoking and risk of hyperemesis gravidarum. To help close that research gap, we performed meta-analysis of the association between smoking and risk of hyperemesis gravidarum.

METHODS

A literature search was carried out in PubMed, Web of Science, and Scopus from the earliest possible year to January 2016. The heterogeneity across studies was explored by Q-test and I statistic. The possibility of publication bias was assessed using Begg's and Egger's tests. The results were reported using odds ratio (OR) estimate with its 95% confidence intervals (CI) using a random-effects model.

RESULTS

The literature search yielded 607 publications until January 2016 with 1 400 000 participants. Based on the random-effects model, compared to nonsmoker people, the estimated OR of hyperemesis gravidarum was 0.40 (95% CI: 0.24, 0.56).

CONCLUSIONS

We showed based on reports in epidemiological studies that smoking before and during pregnancy is not a risk factor for hyperemesis gravidarum but also can reduce the risk of it.