Study finds standard for measuring fetal growth flawed for non-whites

Latino, African-American and Asian babies tend to weigh less at birth than white infants but that doesn’t necessarily mean they are too small even though they might be classified that way, according to a new study from the National Institutes of Health.

The study indicates that the way doctors determine if a fetus is normal sized may be flawed when it comes to non-white babies, because the standard was set based on research done in the 1980s exclusively on pregnant white women.

The researchers tracked more than 2,000 healthy pregnant women from the four major racial and ethnic groups. When the study's authors accounted for external factors, they found that white babies are born the largest, followed by Latino, black and then Asian babies.

Researchers credit genetics and environment for the differences and say the study indicates ultrasound evaluation standards need to be updated to account for the heritage of the fetus.

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"Essentially a one-size-fits-all [standard] for estimating fetal growth isn’t appropriate without considering the mother’s race [and] ethnicity," said lead researcher Germaine Buck Louis, director of the division of intramural population health research at the National Institutes of Health’s Eunice Kennedy Shriver National Institute of Child Health and Human Development.

Source: National Institutes of Health

The study found that under current standards  up to 15 percent of the non-white fetuses in the study would have been misclassified as small for their gestational age. 

"If the wrong standard is being used, then it might be that a fetus is being viewed as under growing or not growing at the optimum rate," Louis said. "And that could lead to more diagnostic evaluation and testing. It could induce some stress for the mom."

Louis said differences in growth start to show around week 10, with varying bone growth among the groups.

According to the federal government, nearly half of all babies born in the U.S. in recent years and more than half of babies born in California have non-white mothers. 

The research for the study took place across the country, including at the University of California, Irvine; Fountain Valley Regional Hospital and Medical Center; and Miller Children’s Hospital/Long Beach Memorial Medical Center.

Louis said more research on this topic is underway, noting that another NIH group is currently conducting a similar study.