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More Women at Risk for Birth Defects Than Thought

But folic acid supplements can greatly reduce risk, researchers report

THURSDAY, May 20, 2004 (HealthDayNews) -- If you're thinking of having a child, your risk for giving birth to a baby with neural tube defects may be greater than you think.

New research shows a genetic variant puts half of all women at increased risk for these conditions. The finding highlights the importance of taking folic acid supplements during pregnancy because they dramatically reduce your risk, the authors of a new study say.

Spina bifida, perhaps the most well-known neural tube defect, is a deformation of the spine and is the leading cause of childhood paralysis in the United States. Anencephaly is the congenital absence of much of the brain and spinal cord; it leads to miscarriage, stillbirth or death shortly after birth.

"It has been known that this particular gene variant, called the MTHFR C677T variant, is linked to spina bifida," said lead researcher Dr. Peadar Kirke, a specialist in public health medicine from the Health Research Board in Dublin, Ireland.

"What's new about this study is if you have only one copy of this variant, it also increases the risk of spina bifida," he added.

Basically, a woman can have one of two variants of this gene, TT or CT. It has been found that women with the TT variant have a 250 percent greater risk of giving birth to a baby with a neural tube defect.

However, the new study showed that women with the CT variant also face a greater risk, in this case 50 percent. The normal form of the gene, CC, is not associated with any increased risk.

"About 38 percent of women have this CT variant," Kirke said, while only 10 percent of women have the TT variant.

In their study, Kirke and his colleagues looked at the genotype of 395 people born with neural tube defects and compared them with 848 healthy people.

Their report appears in the May 22 issue of the British Medical Journal.

"Our findings give a lot of extra weight to the public health recommendation that women should take folic acid," Kirke said.

Both these genotypes are associated with lower levels of folate and higher levels of homocysteine. Taking folic acid supplements can correct this problem and prevent at least 50 percent to 70 percent of these birth defects, the researchers said.

"Neural tube defects arise from a failure of closure of the developing neural tube," Kirke explained. "This is the part of the baby that becomes the spine and the brain."

"Because this happens at about five weeks after a missed period, it is very important that folic acid is taken before you become pregnant," he added. "Taking folic acid after you know you are pregnant will not offer the protection."

"Any woman who could become pregnant should be taking 400 micrograms of folic acid daily, at least a month before becoming pregnant," he stressed. This is in addition to any foods that are fortified with folic acid, such as breakfast cereals.

Richard H. Finnell, director of the Institute of Biosciences and Technology at Texas A&M University, said, "If women of reproductive age took a multivitamin containing folic acid, it would not matter if you were CT, or TT or even CC. It would make any risk from the MTHFR gene disappear."

Dr. Charles C. Duncan, a professor of neurosurgery and pediatrics at Yale University, put it more simply: "If you are thinking of making babies, take folic acid."

More information

The National Institutes of Health can tell you about folic acid, and the March of Dimes can tell you more about birth defects.

SOURCES: Peadar Kirke, M.D., specialist, public health medicine, Health Research Board, Dublin, Ireland; Richard H. Finnell, Ph.D., director, Institute of Biosciences and Technology, and professor, genetics, toxicology and biomedical sciences, Texas A&M University; Charles C. Duncan, M.D., professor, neurosurgery and pediatrics, Yale University, New Haven, Conn.; May 22, 2004, British Medical Journal
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