RESEARCH - Folate Deficiency Associated with Higher Early Miscarriage Risk

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National Institutes of Health

National Institute of Child

Health & Human Development

October 15, 2002

Folate Deficiency Associated with Higher Early Miscarriage Risk

Pregnant women who have low blood levels of the vitamin folate are more

likely to have early miscarriages than are pregnant women who have adequate

folate levels, according to a study of Swedish women by researchers at the

Karolinska Institutet in Sweden and at the National Institute of Child

Health and Human Development (NICHD).

The finding suggests that a 1998 mandate by the U.S. Food and Drug

Administration to fortify grain products with folic acid (the synthetic form

of the vitamin) may prevent miscarriage in some women, in addition to

lowering their risk for having a child with a class of birth defects known

as neural tube defects (NTDs). NTDs include both spina bifida, in which a

piece of the spinal cord protrudes from the spinal column, causing paralysis

below the protrusion, and anencephaly, a fatal condition in which the brain

fails to develop.

The study appears in the current issue of the Journal of the American

Medical Association. The researchers also found that women with high folate

levels are no more likely to have early miscarriages than are women with

moderate, but adequate, folate levels.

" The results of this study reinforce the importance of folate for women in

their childbearing years, " said Duane , M.D., Director of the

NICHD. " Not only does taking folic acid before conception prevent the

devastating form of birth defects known as neural tube defects, but it also

appears to lower the risk of early miscarriage. "

Since January 1998, the U.S. Food and Drug Administration has required food

manufacturers to fortify certain grain products with folic acid, to reduce

the risk of NTDs. Also in 1998, the Institute of Medicine recommended that

all women of childbearing age receive 400 micrograms of folic acid each day.

Folate occurs naturally in beans, leafy green vegetables and citrus fruits.

The study was conducted between 1996 and 1998 in Uppsala County, Sweden by

Lena , M.D., of the Karolinska Institutet in Stockholm, Sweden, and

her colleagues. Sweden was considered an ideal country in which to conduct

this study because, unlike the United States, its grain supply is not

fortified with folic acid, explained the NICHD author of the study,

Mills, M.D., of NICHD's Division of Epidemiology, Statistics, and Prevention

Research. As a result, the researchers were better able to study the

relationship between folate deficiency and miscarriage than they would have

been in the United States, where food fortification has vastly reduced the

rate of folate deficiency.

The researchers compared 468 women who had an early miscarriage (between six

and twelve weeks gestation) to 921 women who were six to twelve weeks

pregnant. The women were asked a series of questions about their

reproductive and health histories. They also provided blood samples that

were used to assess their blood folate levels and smoking status.

The researchers statistically compensated for factors known to influence

miscarriage risk and blood folate level, such as maternal age, education,

maternal smoking, obesity, number of previous pregnancies, and country of

origin. They found that folate deficiency was associated with a fifty

percent increase in risk of early miscarriage. They also found that high

folate levels were not associated with miscarriage risk. The researchers

defined folate deficiency as a blood folate level below 4.9 nmol/L, which is

the cut-off for recommending folic acid supplements in Sweden. Women with

blood folate levels between 5.0 and 8.9 nmol/L were considered to have

adequate folate intakes, while women with folate levels greater than 9.0

nmol/L were considered to have high folate intakes.

Dr. Mills noted, however, American women have higher folate levels than do

Swedish women. According to the 1999 CDC's National Health and Nutrition

Examination Study, the average blood folate level for American women is 16.2

nmol/L.

###

The NICHD is part of the National Institutes of Health, the biomedical

research arm of the federal government. The Institute sponsors research on

development, before and after birth; maternal, child, and family health;

reproductive biology and population issues; and medical rehabilitation.

NICHD publications, as well as information about the Institute, are

available from the NICHD Web site, http://www.nichd.nih.gov, or from the

NICHD Information Resource Center, 1-800-370-2943; E-mail

NICHDInformationResourceCenter@....

http://www.nichd.nih.gov/new/releases/miscarriage_risk.cfm

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