July 18, 2013 -- A high rate of birth defects has confounded Washington health officials, who have been unable to identify a cause.

A report released Tuesday by the Washington State Department of Health said that, since 2010, the neighboring counties of Yakima, Benton and Franklin have an unusually high number pregnancies affected by the birth defect anencephaly, which results in a newborns' brains being severely underdeveloped.

In the U.S., there are approximately one or two expected cases of anencephaly for every 10,000 annual births. However, in the three named Washington counties, with a total population of approximately 515,000, the health department found that there was an abnormally high number of cases reported from January 2010 to January 2013 with approximately eight cases of anencephaly for every 10,000 births.

Anencephaly is a birth defect, almost always fatal, where the neural tubes in the fetus do not close properly. As a result, the forward part the fetus' brain is not developed and the other part of the brain is exposed to amniotic fluid, causing further damage. Most fetuses that develop the defect are stillborn. Those who survive to birth usually die shortly after being born.

Anencephaly can be caused by a pregnant woman lacking enough of the B-vitamin folic acid in her diet. However, local CDC and state health department officials found that there was not a significant difference in the amount of supplemental folic acid taken by women whose pregnancies were affected by the birth defect and those who had healthy pregnancies.

Amniocentesis Can Identify Birth Defects

In addition to looking at supplemental folic health, the department also looked for variations in other risk factors, including family history, pre-pregnancy weight and whether or not the mothers drank water from a private or public source. Officials found no significant differences among the risk factors when comparing anencephaly and healthy births in the region.

Donn Moyer, a spokesman for the Washington State Department of Health, said anencephaly is still an extremely rare disease and finding a common cause for a handful of cases a year can be difficult to determine.

"There's one region in the state [that's had a spike]," said Moyer. "It could be complete coincidence, but we didn't want to shrug our shoulders and [say it's a coincidence.]"

Lifestyle Changes Can Prevent Birth Defects

Moyer said the department would continue to analyze information until at least the end of the year and then reassess the situation after examining 2013 rates of anencephaly in that region.

Dr. Joanne Stone, director of Maternal Fetal Medicine at Mount Sinai Medical Center in New York, said anencephaly can be caused by a combination of genetic and environmental factors and that the increase in cases is worrisome.

"The interesting thing with this study is that they looked at different factors, and women's histories, and obesity, and at medical history and couldn't find anything that stood out," said Stone. "Could it be a fluke? We don't know. It could take time to uncover some sort of [unusual] exposure."

The U.S. Preventive Services Task Force recommends women of child-bearing age should take 400-1,000 micrograms of folic acid every day. According to Stone, women with higher risk factors for anencephaly, such as diabetes or a family history of neural tube defects, should take anywhere between 4 to 5 milligrams of folic acid.