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New way of measuring neonatal mortality uncovers 'paradoxical' racial disparity

April 24, 2023
by Matt Kristoffersen

When it comes to gauging the mortality rate of newborn babies born preterm, methods matter, researchers at the Yale School of Public Health (YSPH) have found.

In a new research letter published in JAMA Pediatrics, a team of researchers from YSPH and Yale School of Medicine found that using a different methodological approach revealed a “paradoxical” racial disparity.

By measuring based only on the number of live-born extreme, very, or moderate-to-late preterm births, they found that Black babies had a lower rate of neonatal mortality than white babies – a conclusion that goes against the knowledge that Black babies have a higher neonatal mortality rate compared to white, based on the number of all live births. Focusing solely on birth-based measurements among preterm neonates, they said, “may mask racial disparities.”

“We think this is important to report,” said PhD Candidate Bohao Wu (chronic disease epidemiology). “The birth-based method’s results are not consistent with our understanding of the whole population. We wanted to check why this happened.”

The difference in statistical approaches lies in the way the rate of neonatal mortality is determined. Epidemiologists using the fetuses-at-risk method would count ongoing pregnancies along with births. Using that strategy, the researchers calculated that the neonatal mortality rate for Black babies born extremely prematurely was about three times higher than the rate for white babies.

Wu’s team has a possible answer for the “paradox” in the birth-based method. Perhaps more preterm babies without congenital anomalies are born among Black mothers than among white mothers. Then, without statistically controlling for this difference, the results can end up showing that Black babies have lower mortality rates at the most extreme preterm stages.

The birth-based method is not incorrect, they cautioned. “Paradoxical result can arise in epidemiological research, and we need to explore why this happens,” Wu said.

The research letter is the first to compare the two methodological approaches to neonatal mortality rates side-by-side. That way, epidemiologists can understand how the methods can end up reaching vastly different conclusions.

Still, the researchers recommend the fetuses-at-risk method in gestational-age-specific perinatal research because it better reflects known racial disparities among preterm births.

In addition to Wu, Yale researchers contributing to this project are Sarah N. Taylor, Veronika Shabanova, and Nicola Hawley.

Submitted by Jane E. Dee on April 25, 2023