A new research suggests that obese pregnant women have higher odds of having a baby with kidney and urinary tract birth defects.
According with lead researcher Dr. Ian Macumber, a pediatric nephrology fellow at Seattle Children’s Hospital those defects include being born with a single kidney, having kidney swelling or enlarged ureters, which are the tubes that propel urine from the kidneys to the urinary bladder.
The study consisted in analyzing medical charts, including birth and hospital discharge records, from 2003 to 2012. The researchers found more than 3,200 cases of abnormal kidney or urinary tract problems and compared them with more than 13,000 ‘controls’ (newborns without the abnormalities).
When analyzing mother’s pre-pregnancy weight records, the researchers found that mothers who delivered children with the birth defects were almost 1.3 times more likely to be obese than those whose infants didn’t have the kidney and urinary tract defects. The results show a link between maternal obesity and kidney and urinary tract birth defects, but the study did not establish a cause-and-effect relationship.
“There is certainly some question as to whether insulin may play a role in this.” Pregnant women who are overweight may have insulin resistance, a condition in which the body doesn’t respond well to the hormone insulin, and blood sugar is less able to get to the cells, Macumber said.
To define obesity, the researchers were based on the body-mass index (BMI), a measure of relative weight, calculated by dividing individual’s body mass by the square of their height, with kg/m2 units. They use the categories established by the World Health Organization (WHO), which classify a person with a BMI of less than 18.5 as underweight, with a BMI greater than 25 as overweight and above 30 as obese.
More than half of pregnant women in the United States are overweight or obese, and 8 percent of reproductive-aged women are extremely obese, according with the American College of Obstetricians and Gynecologists.
“The more we find out about obesity, the more we find out what a public health problem it is,” Macumber said.
Previous research has linked maternal obesity with newborn heart defects, neural tube defects such as spina bifida and other health conditions. This is the first time it has being found a link with urinary system birth defects.
The kinds of defects Macumber and his colleagues evaluated are diagnosed in up to 1 percent of pregnancies, with some conditions more serious than others. The defects account for about 20 percent or 30 percent of all prenatal abnormalities. The researchers, however, couldn’t determine which defects were most common or how severe they were because they went by hospital codes.
Mendez said that chart reading, while limited in some respects, “is a vital research tool” and a good starting point.
Ideally, future research would follow mothers during pregnancy, tracking their weight and the health of their newborns, looking at the link from the start, he said.
Macumber is to present the findings Nov. 14 at a meeting of the American Society of Nephrology in Philadelphia. Studies presented at medical meetings are typically viewed as preliminary until published in a peer-reviewed journal.
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