LOS ANGELES — Obesity, like cardiovascular disease risk, can originate in the womb, a phenomenon that could have important implications in managing the current obesity epidemic, Dr. Thomas R. Moore said at a meeting of the Obstetrical and Gynecological Assembly of Southern California.
Much evidence now indicates that infants born to mothers with diabetes are likely to become overweight children and adults. They are also more likely to develop gestational diabetes and possibly diabetes as adults.
However, the evidence also seems to suggest that infants born underweight may face a similar risk of obesity and are more likely to experience cardiovascular disease, said Dr. Moore, the chairman of the department of reproductive medicine at the University of California, San Diego.
With regard to the association between a diabetic mother and later obesity in the child, Dr. Moore cited a study of the Pima Indians of Arizona, who have been followed closely in a study since 1965 and among whom there is a high rate of obesity and diabetes.
In that study, the investigators looked at siblings in families with a mother who was diabetic. They compared siblings born before the mother was diagnosed as diabetic with siblings born after her diagnosis.
In 19 families in which one sibling had diabetes and the other did not, 15 of the diabetic children were born after their mother's diagnosis, and only 4 were born before the mother's diagnosis (Diabetes 2000;49:2208-11).
There was no difference in the number of siblings with diabetes in those families born before or after a father's diabetes diagnosis.
The siblings who were exposed to intrauterine diabetes also were a mean 2.6 kg/m2 heavier than were their nonexposed siblings.
In another study linking heaviness and diabetes in the child to that in the mother, Norwegian investigators looked at almost 140,000 women who had given birth.
They found that the rate of gestational diabetes among the women was 31/1,000 in those whose own mothers had diabetes when they were born, compared with a rate of 4/1,000 in those whose own mothers did not have diabetes (BMJ 2000;321:546-47).
Dr. Moore said that in his own practice, he is careful to measure and record body mass index, not just weight, and to help patients who want to lose weight before conception.
Moreover, when he manages maternal diabetes in pregnancy, he is mindful that it can have critical implications for the life of the infant.
“I actually believe I'm making a difference in the adult health of the fetus, who I am helping to treat through the mother by optimizing glucose control,” he said.
In reference to the risks facing underweight newborns, Dr. Moore said that most of the data come from epidemiologic studies that show those infants are more likely to develop high insulin levels, hypertension, diabetes, stroke, and heart disease.
He said that the theory explaining this phenomenon, the “thrifty phenotype,” asserts that when a fetus is growth or nutrient restricted, it shunts nutrients to the most essential organs.
One of the mechanisms the fetus body uses to prevent nutrients from going to less essential systems, such as the musculature, is by making those systems insulin resistant. This insulin resistance persists after birth and predisposes the individual to the conditions associated with metabolic syndrome.
The theory calls into question the common practice in neonatal nurseries of trying to get as many calories as possible into underweight infants in an effort to get them to gain weight quickly, said Dr. Moore.