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NEW YORK (Reuters Health) - Women who are obese before they
become pregnant may be at increased risk of having a baby with
defects of the brain and spinal cord, especially if they tend
to put on weight around the waist, according to new research
from the March of Dimes.
But a woman's body mass index (BMI) before pregnancy had no
relationship to her likelihood of having a child with certain
types of heart malformation, Drs. Gary M. Shaw and Susan
Carmichael of the Children's Hospital Oakland Research
Institute in California found.
Previous studies have linked maternal obesity to a number
of birth defects, especially neural tube defects, which are
malformations of the brain and spinal cord, Shaw and Carmichael
note in the journal Epidemiology. The most common neural tube
defects are spina bifida, in which the spinal cord fails to
close completely during fetal development, and anencephaly, in
which part or all of the brain doesn't develop.
To examine the relationship between obesity and other
weight-related factors in the risk of these and other birth
defects, the researchers looked at 700 women who gave birth to
healthy children and 659 who delivered babies with spina
bifida, anencephaly, a type of heart malformation called
transposition of great arteries, or a different heart defect
known as tetralogy of Fallot.
There was no association with prepregnancy BMI and either
heart defect. Women with BMIs of 30 or greater were 60 percent
more likely to have a child with anencephaly and 40 percent
more likely to have a baby with spina bifida than their slimmer
peers. But babies born to mothers who said that they had gained
weight around their waists rather than their hips were 2.4
times as likely to have anencephaly and at 1.8 fold greater
risk of spina bifida.
Abdominal weight gain may play a role in the development of
type 2 diabetes, the researchers note. "Thus, this finding may
offer a clue to underlying mechanisms for the associations of
obesity with birth defect risk, given that clinical diabetes is
also a risk factor for birth defects," they write.
SOURCE: Epidemiology, July 2008.
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