Fetuses of minority mothers may be at risk for being misdiagnosed as being too small, according to a recent study by the National Institutes of Health and other organizations.
The study, published online Sept. 29 in the American Journal of Obstetrics and Gynecology, showed although many fetuses of minority moms are developing normally, hereditary and environmental factors could be making them smaller than their white counterparts.This could cause a mother having an otherwise healthy pregnancy, to undergo a series of unnecessary tests and procedures, researchers found.
Researchers used serial scans of more than 1,700 low-risk pregnancies, pointing out that many practitioners are looking at older reference charts when determining whether a fetus is growing normally, according to an NIH news release. Of the 1,737 participants in the study, 26% were white, 26% black, 28% Hispanic and 20% Asian.
Study participants had a total of five sonograms between the 16th through the 41st week of pregnancy, the news release said, with researchers averaging measurements from all the sonograms to create a sequence of estimated fetal weights. Notable differences were found in different groups after the 20th week of gestation, with white mothers having the largest fetuses at 4,402 grams, fetuses of Hispanic mothers at 4,226 grams. Black mothers had the smallest fetuses at 4,053 grams, according to the news release.
When scoring the estimated weights of fetuses of minority mothers, based on weights compiled for fetuses of white mothers, researchers found that 5 to 15% of fetuses of minority mothers were below the 5th percentile when compared to white mothers. In the 35th week of pregnancy, 14 percent of fetuses of black mothers and 15% of fetuses of Asian mothers would have been categorized as being below the 5th percentile based on the white standard, the news release stated.
Fetuses are measured during ultrasound exams during which healthcare providers measure head circumference, abdominal circumference and the length of the femur or thigh bone. Growth chart weights often used are based on a 1980s study by Frank Hadlock and his team, who looked at ultrasound measurements of 139 pregnancies of mostly white, middle class women, the NIH release said.
But these days, according to the study, new mothers are older, heavier and more likely to be non-white than in past years.
“Doctors like to be proactive — if they suspect there’s a problem with a fetus’ growth, then they’re likely going to order tests and investigate,” said the study’s first author, Germaine Buck Louis, Ph.D, Director of the Division of Intramural Population Health Research at NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development. “But inaccurate standards may be leading women to receive unnecessary tests — not to mention the stress of thinking something may be wrong — when their pregnancies actually are on track.”
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