Somali-Born Women Have Lowest Preterm Birth Rate in Ohio

Year after year, studies have found that non-Hispanic white women have the lowest preterm birth rate in Ohio, but new research found a different trend.

Somali immigrants had a 5.9 percent preterm birth rate in the state from 2000 to 2015 compared to 7.9 percent for U.S.-born, non-Hispanic white women, investigators from Nationwide Children’s Hospital report.

The finding is surprising, says Irina Buhimschi, MD, an obstetrician/gynecologist, director of the Center for Perinatal Research at The Research Institute at Nationwide Children’s and study author. But more importantly, “this serves as a starting point for more targeted studies aimed at learning why the rate is different and how that can be applied to reduce prematurity in the general population.”

Preterm birth is the second leading cause of infant mortality, can hinder intellectual and physical development and cause a long list of long-term problems including cerebral palsy, autism, behavioral problems, vision and hearing loss, and asthma. It’s also associated with cardiovascular disease and Alzheimer’s disease later in life.

The researchers hope this study, published in Obstetrics & Gynecology, also launches more that will explain and close the persistent disparity in premature births between non-Hispanic white and non-Hispanic black women in Ohio and nationally.

The researchers analyzed state and hospital records of nearly 2 million births in Ohio. In addition to Somalis, the researchers broke out births by other African-born black women, whose prematurity rate was 8.4 percent over the 15 years. Consistent with past studies, U.S.-born non-Hispanic black women had the highest rate, at 13 percent.

“We don’t know why, but historically the United States has a higher rate of premature births than other developed countries,” says Dr. Buhimschi, who is also a professor of Pediatrics and Obstetrics/Gynecology at the Ohio State University College of Medicine. “And, why a racial disparity persists is unknown.”

Dr. Buhimschi’s fellow researchers are now studying the birth records in other states that have large Somali immigrant populations, to see if the trend is consistent. The Ohio investigators are also recruiting Somali women for studies they hope will reveal why they have the lowest rate here, and whether the rate persists as the population becomes acclimated to the United States.

“When Hispanics first came here, they had low preterm birth rates but over time, their rates climbed,” Dr. Buhimischi says. “They seemed to have had some protection against prematurity that was lost.”

Along with their low preterm rate, Somali women had the highest post-term birth rate at 5.8 percent compared to less than 1 percent for the other groups, the study found.

“It seems they have a pattern of extended pregnancy, but we don’t know if post-term birth is a positive or a negative or a tradeoff,” Dr. Buhimschi says.

She suggests that the explanation for the differences in preterm rates is likely genetic and environmental. “Some studies suggest the genome harbors areas susceptible to environmental influences.”

In addition to studying the genes of the Somali women, in upcoming studies, the researchers plan to look at factors such as diet, stress and lifestyle.

Reference:

Oliver EA, Klebanoff M, Yossef-Salameh, Oza-Frank R, Moosavinasab S, Reagan P, Muglia L, Buhimschi C, Buhimschi I. Preterm birth and gestational length in four race-nativity groups, including Somali Americans. Obstetrics & Gynecology. 2018 Jan 9. [Epub ahead of print]

Photo credit: Nationwide Children’s