Preterm birth rates vary across nativity, ethnicity and racial identities

Key takeaways:

• U.S.-born women across racial and ethnic groups had a greater preterm birth rate vs. non-U.S.-born counterparts.
• All minoritized groups had increased extremely preterm birth risk vs. U.S.-born white women.

Risks for preterm birth overall and by gestational age varied for women across all nativity, ethnicity and racial identities, according to a retrospective national cohort study published in JAMA Network Open.

“The immigrant paradox is an epidemiologic observation suggesting that non-U.S.-born racial and ethnic groups have better health outcomes, particularly birth outcomes, than their in-country-born counterparts despite experiencing socioeconomic and health care access-related barriers,” Alejandra Barreto, MPH, research data analyst in the division of neonatology at Children’s Hospital of Philadelphia, and colleagues wrote. “However, recent literature has found heterogeneity of perinatal outcomes within immigrant communities by race, ethnicity and country of origin.”

Barreto and colleagues evaluated U.S. National Vital Statistics System birth certificate data from 34,468,901 singleton live births (mean maternal age at delivery, 28 years) from 2009 to 2018. Researchers categorized women as non-U.S.-born and U.S.-born Hispanic, American Indian or Alaska Native, Asian, Black, Native Hawaiian or other Pacific Islander, white and other race/ethnicity.

Primary outcome was preterm birth overall and by gestational category of extremely preterm (< 29 weeks gestation), moderately preterm (29-33 weeks gestation) and late preterm (34-36 weeks gestation) for each subgroup compared with U.S.-born white women.

For all U.S.-born women, Black women had the greatest overall preterm birth rate (12.1%) and white women had the lowest rate (7.2%). For all non-U.S.-born women, Native Hawaiian or other Pacific Islander women had the highest overall preterm birth rate (9.8%) and white women had the lowest rate (5.5%), according to the researchers.

All U.S.-born groups had a greater preterm birth rate compared with non-U.S.-born counterparts. Non-U.S.-born white women (adjusted RR = 0.85; 95% CI, 0.84-0.86) and non-U.S.-born Hispanic (aRR = 0.98; 95% CI, 0.97-0.98) women had significantly decreased overall preterm birth risks compared with U.S.-born white women, the researchers wrote.

Non-U.S.-born Native Hawaiian or other Pacific Islander women had significantly increased risks for overall (aRR = 1.07; 95% CI, 1.01-1.14), moderately (aRR = 1.1; 95% CI, 0.92-1.3) and late (aRR = 1.11; 95% CI, 1.02-1.22) preterm birth compared with U.S.-born counterparts.

Researchers observed increased risks for extremely preterm birth among all racially and ethnically minoritized groups compared with U.S.-born white women. Based on nativity, extremely preterm birth rates were similar for almost all groups; however, U.S.-born Black women had nearly 50% greater rates of extremely preterm birth compared with non-U.S.-born Black women (1.6% and 1.1%, respectively). For minoritized groups, extremely preterm birth risks varied from a mildly increased risk among non-U.S.-born Asian women (aRR = 1.17; 95% CI, 1.14-1.2) to a more substantially increased risk among U.S.-born Black women (aRR = 3.02; 95% CI, 2.99-3.06).

Non-U.S.-born Hispanic women were the only group with a similar moderately preterm birth risk as U.S.-born white women (aRR = 1.01; 95% CI, 1-1.02). Non-U.S.-born women had higher moderately (1.8% vs. 1.6%; P < .001) and late preterm (7.4% vs. 6.4%; P < .001) rates compared with U.S.-born women. Non-U.S.-born Hispanic (aRR = 0.95; 95% CI, 0.94-0.95), white (aRR = 0.85; 95% CI, 0.84-0.86) and Black (aRR = 0.95; 95% CI, 0.94-0.96) women had decreased risk for late preterm birth compared with U.S.-born white women.

“Future studies could explore how nativity, ethnicity and race studied together may represent a way to measure the implications of intersectional structural discrimination associated with racism, colorism and xenophobia for birth outcomes,” the researchers wrote. “In addition, detailed epidemiologic data such as the data presented here could aid preterm birth prevention efforts by informing the design of targeted interventions and policies to improve perinatal outcomes in specific populations.”