Pregnant women who have low blood levels of the vitaminfolate are more likely to have early miscarriages thanpregnant women with adequate folate levels, accordingto a study of Swedish women by researchers at theKarolinska Institutet in Sweden and at the US' NationalInstitute of Child Health and Human Development (NICHD).
The finding suggests that a 1998 mandate by the US Foodand Drug Administration to fortify grain products withfolic acid (the synthetic form of the vitamin) may preventmiscarriage in some women, in addition to lowering theirrisk for having a child with a class of birth defects knownas neural tube defects (NTDs). NTDs include both spinabifida and anencephaly, a fatal condition in which the brain failsto develop.
The study appears in the current issue of the Journal ofthe American Medical Association. The researchers alsofound that women with high folate levels are no more likelyto have early miscarriages than are women with moderate,but adequate, folate levels. Folate occurs naturally in beans, leafygreen vegetables and citrus fruits.
"The results of this study reinforce the importance offolate for women in their childbearing years," said DuaneAlexander, director of the NICHD. "Not only doestaking folic acid before conception prevent the devastatingform of birth defects known as neural tube defects, but italso appears to lower the risk of early miscarriage."
Since January 1998, the US Food and Drug Administrationhas required food manufacturers to fortify certain grainproducts with folic acid, to reduce the risk of NTDs. Alsoin 1998, the Institute of Medicine recommended that allwomen of childbearing age receive 400 micrograms of folicacid each day. Canada and Chile also have fortification programmes in place, but European countries have been hesitant about adopting the practice. In the UK, for example, the Food Standards Agency recently decided not to recommend the fortification of grain on the grounds that not enough was known about the potential adverse effects.
The study was conducted between 1996 and 1998 in UppsalaCounty, Sweden, by Dr Lena George of the KarolinskaInstitutet in Stockholm, Sweden, and her colleagues.Sweden was considered an ideal country in which to conductthis study because, unlike the United States, its grainsupply is not fortified with folic acid, explained the author of the study, Dr James Mills of NICHD's division of Epidemiology, Statistics, and PreventionResearch.
The researchers compared 468 women who had an earlymiscarriage (between six and 12 weeks gestation) to 921women who were six to 12 weeks pregnant. The womenwere asked a series of questions about their reproductiveand health histories. They also provided blood samplesthat were used to assess their blood folate levels andsmoking status.
The researchers statistically compensated for factors knownto influence miscarriage risk and blood folate level, suchas maternal age, education, maternal smoking, obesity,number of previous pregnancies, and country of origin.They found that folate deficiency was associated with a50 per cent increase in risk of early miscarriage. Theyalso found that high folate levels were not associated withmiscarriage risk.
The researchers defined folate deficiency as a blood folate level below 4.9 nmol/L, whichis the cut-off for recommending folic acid supplements inSweden. Women with blood folate levels between 5.0 and 8.9nmol/L were considered to have adequate folate intakes,while women with folate levels greater than 9.0 nmol/L wereconsidered to have high folate intakes.
Mills noted, however, that American women have higher folatelevels than do Swedish women. According to the 1999 CDC'sNational Health and Nutrition Examination Study, theaverage blood folate level for American women is 16.2nmol/L.
The NICHD is part of the US National Institutes of Health, thebiomedical research arm of the US federal government. TheInstitute sponsors research on development, before andafter birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation.