Morbidity and Mortality Weekly Report, New York: By now, most women probably know that adequate levels of folate are important to prevent a major pregnancy complication but in recent years folate levels have decreased among non-pregnant US women of childbearing age, according to a new report.

In order to prevent neural tube birth defects like spinabifida, mandatory fortification of cereal-grain products with folate or folic acid was instituted in the US in 1998, researchers from the Centers for Disease Control and Prevention note in the agency's Morbidity and Mortality Weekly Report.

An earlier study suggested that this program was successful in raising folate levels in women who might become pregnant. In the present study, data from two national surveys, conducted in 1999-2000 and 2003-2004, were analysed to assess current trends.

During the interval between the surveys, average blood levels of folate fell 16%.

The authors suggest four possible reasons for the decline

1. A reduction in the proportion of women taking folate supplements
2. A drop in intake of folate-fortified foods orthose naturally rich in folate
3. Variations in the amount of folate added to foods since fortification became mandatory
4. Increases in risk factors, such as obesity, that are linked todecreased folate levels

At present, it is recommended that women of childbearing age "consume at least 400 micrograms of folic acid daily through dietary supplements and fortified foods, in addition to a diet containing folate-rich foods," the report states.