Association between maternal prepregnancy body mass index and risk of preterm birth in more than 1 million Asian American mothers.

Among Asian American mothers, maternal prepregnancy overweight or obesity, defined by Asian-specific, lower BMI cutoffs, was significantly associated with an increased risk of preterm birth. The risk of preterm birth increased with increasing obesity severity. These findings highlight the importance of using Asian-specific BMI cutoffs in assessing risk of preterm birth among Asian American mothers.