Smoking may induce pregnancy loss

Smoking appears to be a risk factor for pregnancy loss, according to the results of a Mendelian randomization study. Meanwhile, there are no clear associations seen for moderate alcohol and coffee intake.

The analysis included 60,565 women with pregnancy loss and 130,687 women with live birth (controls) from the UK Biobank study, and 3,312 and 64,578 women, respectively, from the FinnGen consortium. Pregnancy loss was defined as stillbirth, spontaneous miscarriage, or termination.

Researchers used 314, 84, and 12 single-nucleotide polymorphisms (SNPs) associated with smoking initiation and alcohol and coffee consumption, respectively.

In both UK Biobank and FinnGen cohorts, genetic predisposition to smoking initiation was associated with a heightened risk of pregnancy loss. The fixed-effects meta-analysis showed that each one standard deviation-increase in the prevalence of smoking initiation conferred a 31-percent risk increase (combined odds ratio [OR], 1.31 (95 percent confidence interval [CI], 1.25–1.37).

On the other hand, pregnancy loss showed no significant relationship with genetically predicted consumption of alcohol (OR, 1.09, 95 percent CI, 0.93–1.27) or coffee (OR, 0.96, 95 percent CI, 0.87–1.06).

The finding on smoking in relation to pregnancy loss is consistent with most previous studies. [Am J Epidemiol 2014;179:807-823; Tob Control 2015;24:328-335]

Therefore, the researchers called for initiatives aimed at reducing the prevalence of smoking and promoting cessation in couples preparing pregnancy. On the other hand, more studies are needed to establish the safety of moderate alcohol and coffee consumption on pregnancy outcomes.