Boston – New research findings from Boston Medical Center show that women born in the United States have an increased risk of experiencing adverse perinatal outcomes including preterm birth, hypertensive disorders, low birth weight and NICU admission, compared to women born outside of the U.S. Published in the Maternal and Child Health Journal, the results show a greater impact of nativity, or place of birth, on the outcomes for all mothers and their babies, and highlight how these are particularly pronounced among Black mothers and their infants.

There was an overall increase of risk to women born in the U.S. compared to abroad. Study results showed that 10.6 percent of women born in the U.S. experienced preterm birth compared to 8.2 percent of foreign-born women. The prevalence of early preterm birth (at or before 32 weeks of pregnancy) and low birth weight at term were more than twice as high for those born in the U.S. 

The study emphasizes the racial and ethnic disparities in birth outcomes and the impact of race-based inequities in healthcare. Black women born in the U.S. experienced a 22 percent higher prevalence of hypertensive disorders, 28 percent higher prevalence of preterm birth and 83 percent increased prevalence of early preterm birth compared to White women.

“Differences in birth outcomes based on maternal birthplace do not uniformly apply when race and ethnicity are considered,” says Tejumola Adegoke, MD, MPH, an obstetrics & gynecology physician and director of equity and inclusion at Boston Medical Center. “Our data suggests that the health advantage previously noted among migrants to the United States is attenuated for Black birthing people and their children. This underscores the impact of race-based discrimination and differences in care. As we understand the factors that impact maternal inequities better, we can use that to combat disparities and improve outcomes for all women.”

The prevalence of preterm birth was highest among U.S.-born Black women at 12 percent, and U.S. - born Hispanic women at 10 percent. However, the largest association between women being U.S.-born and experiencing adverse outcomes was among White women where there was a 40 percent increased prevalence of hypertensive disorders and similar prevalence of preterm delivery, diabetes, and cesarean delivery and NICU admission.

To examine the association between nativity and both outcomes within racial and ethnic groups, as well as racial and ethnic differences within nativity groups, researchers studied a large sample of 11,097 women including 3,476 women born in the U.S. and 7,621 women who were foreign-born including naturalized citizens, temporary migrants, refugees, asylum-seekers, undocumented immigrants, and permanent residents with varying lengths of stay in the U.S. The study was done using the electronic health records of all births of at least 20-week gestation that occurred from January 1, 2010 to March 31, 2015 at Boston Medical Center.

The retrospective study of patients includes a large cohort of women with substance use disorder (SUD), who have been noted to have a higher risk of maternal and neonatal morbidity. Researchers used a sensitivity analysis to exclude women with SUD for part of this study, who were mostly U.S.-born and White, and found that the disparity between U.S.-born Black and White women widens substantially. Since substance use in pregnancy is known to adversely impact birth outcomes, this analysis demonstrates the true extent of the racial inequity in this study population, which might otherwise be obscured.

Among those who were foreign-born, Black women still had a higher prevalence of many maternal and neonatal complications, while Hispanic women had a lower prevalence of complications, compared to White women. Black women and infants consistently experienced worse outcomes regardless of their nativity, while foreign-born Hispanic women experienced less disparate outcomes.

“The system of race-based segregation and discrimination in the United States affects access to all social and economic resources including healthcare,” says Adegoke, also an assistant professor of obstetrics & gynecology at Boston University School of Medicine. “Individuals who have lived outside of this system for some time may temporarily avoid the cumulative effect of racism and its related stress on their health, but for Black women, the effect on maternal mortality and perinatal outcomes is seemingly inescapable.”

Future research should continue to assess the best practices for addressing modifiable risk factors for perinatal outcomes, including systemic racism and disparate care provisions. According to the study authors, the focus should be on innovative interventions targeted to at-risk populations.


About Boston Medical Center

Boston Medical Center (BMC) is a private, not-for-profit, 514-bed, academic medical center that is the primary teaching affiliate of Boston University School of Medicine. It is the largest and busiest provider of trauma and emergency services in New England. BMC offers specialized care for complex health problems and is a leading research institution, receiving more than $166 million in sponsored research funding in fiscal year 2019. It is the 13th largest funding recipient in the U.S. from the National Institutes of Health among independent hospitals. In 1997, BMC founded Boston Medical Center Health Plan, Inc., now one of the top ranked Medicaid MCOs in the country, as a non-profit managed care organization. Boston Medical Center and Boston University School of Medicine are partners in Boston HealthNet – 12 community health centers focused on providing exceptional health care to residents of Boston. For more information, please visit

Media Contact:
Return to BMC News