Daily Multivitamins Prevent Birth Defects

TORONTO, Aug. 31 -- If all women of child-bearing age took a daily dose of folic-acid fortified multivitamins, they would sharply reduce the risk of several major birth defects, researchers here concluded.

A meta-analysis of 41 studies showed that a daily multivitamin reduces the risk of neural tube, cardiovascular and limb defects, as well as oral clefts, cleft palate, urinary tract abnormalities, and congenital hydrocephalus, according to Gideon Koren, M.D., of the University of Toronto.

"Clearly, this information is very important for any woman looking to give her baby the healthiest start possible," Dr. Koren said.

Dr. Koren noted that the addition of folate supplements to the North American diet has reduced the incidence of neural tube defects, and there have been hints that regular use of other dietary supplements might prevent other birth abnormalities.

But the current study, reported in the August issue of the Journal of Obstetrics and Gynaecology of Canada, is the first to take a systematic look at the issue. Dr. Koren and colleagues said.

The researchers found 27 case control studies, four randomized controlled trials, and 10 cohort studies that reported on a range of birth abnormalities. The daily use of a folic-acid fortified multivitamins -- in case-control studies, and in cohort and randomized trials, respectively -- led to a:

• A 33% and a 48% reduction in neural-tube defects.
• A 23% and a 39% drop in cardiovascular defects.
• A 52% and a 43% per cent lower rate of limb deformities.
• A 24% and a 58% reduction in cases of cleft palate.
• A 37% and a 42% reduction in oral cleft with or without cleft palate.
• A 52% and a 32% decrease in urinary-tract defects.

All of the protective effects were statistically significant, the researchers said.

Case-control studies showed a significant protective effect for hydrocephalus, with a hazard ratio of 0.37 (and a 95% confidence interval from 0.24 to 0.56) but the randomized and cohort studies showed a non-significant trend in the other direction, with a hazard ratio of 1.54.

The vitamins supplements had no preventive effect on Down's syndrome, pyloric stenosis, undescended testis, or hypospadias, the researchers said.

"We've known for over a decade that taking folic acid before and during pregnancy can help prevent neural tube defects," said Donald Davis, M.D., president of the Society of Obstetricians and Gynaecologists of Canada, which publishes the journal.

"But in general there's still a lot we don't know about what causes birth defects and how we can prevent them," he said. "This study fills a gap in that we can now offer women some concrete advice. We can say, 'look, this is one way you can help prevent these.'"

Dr. Koren and colleagues said the study suggested that, along with folate, other vitamins should be added to the food supply. "Serious consideration should be given to fortification of flour or other food staples with other vitamins in addition to folate," they argued.