Trends in gestational diabetes mellitus among nulliparous pregnant individuals with singleton live births in the United States between 2011 to 2019: an age-period-cohort analysis

BACKGROUND: The rate of gestational diabetes mellitus has increased over the past decade. An age, period, and cohort epidemiologic analysis can be used to understand how and why disease trends have changed over time. OBJECTIVE: This study aimed to estimate the associations of age (at delivery), period (delivery year), and cohort (birth year) of the pregnant individual with trends in the incidence of gestational diabetes mellitus in the United States. STUDY DESIGN: We conducted an age, period, and cohort analysis of nulliparous pregnant adults aged 18 to 44 years with singleton live births from the National Vital Statistics System from 2011 to 2019. Generalized linear mixed models were used to calculate the adjusted rate ratios for the incidence of gestational diabetes mellitus for each 3-year maternal age span, period, and cohort group compared with the reference group for each. We repeated the analyses with stratification according to self-reported racial and ethnic group (non-Hispanic Asian-Pacific Islander, non-Hispanic Black, Hispanic, and non-Hispanic White) because of differences in the incidence of and risk factors for gestational diabetes mellitus by race and ethnicity. RESULTS: Among 11,897,766 pregnant individuals, 5.2% had gestational diabetes mellitus. The incidence of gestational diabetes mellitus was higher with increasing 3-year maternal age span, among those in the more recent delivery period, and among the younger birth cohort. For example, individuals aged 42 to 44 years at delivery had a 5-fold higher risk for gestational diabetes mellitus than those aged 18 to 20 years (adjusted rate ratio, 5.57; 95% confidence interval, 5.43–5.72) after adjusting for cohort and period. Individuals who delivered between 2017 and 2019 were at higher risk for gestational diabetes mellitus than those who delivered between 2011 and 2013 (adjusted rate ratio, 1.24; 95% confidence interval, 1.23–1.25) after adjusting for age and cohort. Individuals born between 1999 and 2001 had a 3-fold higher risk for gestational diabetes mellitus than those born between 1969 and 1971 (adjusted rate ratio, 3.12; 95% confidence interval, 2.87–3.39) after adjusting for age and period. Similar age, period, and cohort effects were observed for the assessed racial and ethnic groups, with the greatest period effects observed among Asian and Pacific Islander individuals. CONCLUSION: Period and birth cohort effects have contributed to the rising incidence of gestational diabetes mellitus in the United States from 2011 to 2019.