While folic acid is needed for all women of child-bearing age, there’s one group in particular that needs both awareness and access to the supplement more than others.

According to a new study, less than 5-percent of low-income urban mothers took daily folic acid supplements before getting pregnant. That is despite the efforts of numerous local and national health organizations to promote the importance of folic acid in the fight to prevent potentially crippling birth defects.

“The findings are concerning because they show that public health interventions aren’t always effective in reaching vulnerable populations who need them the most,” said Dr. Tina Cheng, co-director ofJohn HopkinsChildren’s Center and the study’s lead author.

The neural tube is completely developed just 28 days after conception, often before a woman knows she is pregnant. Because nearly half of all U.S. pregnancies are unplanned, all women of child-bearing age are recommended to routinely take folic acid supplements daily.

Since 1992, The U.S. Public Health Service has recommended that all women of reproductive age take folic acid supplements. The vitamin B9 has been found to reduce the rate of neural tube defects by up to 70-percent.

For the study, researchers collected data on nearly 8,500 low-income mothers and their children, then followed more than 7,600 of the women who had one child without birth defects.

Among all of the women, only 4-percent took folic acid supplements daily before becoming pregnant. Overall, nearly 87-percent of the mothers didn’t take any prenatal vitamins before conception.

The study included white, black, and Hispanic women, women who were married or single, those with and without a college education, those who smoked, drank, and didn’t, and women whose pregnancy was planned or unplanned.

The study isn’t perfect. Dr. Cheng and the team acknowledge that the study is limited in its focus on one city (Boston), so the finding may not apply generally. In addition, the women in the study self-reported their use of vitamin supplements.

Dr. Cheng does say that the findings are an important step in understanding folate supplement levels in vulnerable populations, as well as helping to develop strategies to reduce health disparities.

The report was published recently in the American Journal of Public Health.