Women who deliver twins are more likely to smoke and have high frequencies of specific SNPs: Results from a sample of African-American women who delivered preterm, low birth weight babies.

Objectives: We examine if there are genetic and environmental differences between mothers of singleton and multiple pregnancies in a sample of African-American mothers.

Methods: We focus on genomic areas suggested to increase or decrease the odds of multiple pregnancies. We computed the odds ratio (OR) and the 95% confidence interval (CI) for each SNP unadjusted or adjusted with smoking.