Cases of rare, fatal birth defects continue to appear at higher-than-expected levels in some portions of Washington state, with at least seven babies born in 2013 with anencephaly in the Yakima, Benton and Franklin counties of that state.
The rate of the birth defect, which results in babies being born without parts of their brains or skulls, was three times the national average for areas with similar populations.
Investigators have previously looked at the high rates seen in these areas of the state, and were unable to find a cause for the Washington birth defect cluster.
Local medical experts and mothers say the investigations have included very little ground work in the affect areas however, and are calling for additional actions as the number of children born with anencephaly appears to be continuing.
There have been 30 cases of anencephaly in the area since 2010, giving it a rate of 8.7 cases per 10,000 births. That compares with just 2.1 cases per 10,000 births nationwide.
CDC officials told NBC News that they hoped that the cases had been a statistical anomaly, but the continuing high prevalence has them worried.
While no culprit has yet been determined, health experts say they have seen low rates of folic acid supplementation in the area, which can increase the risk of anencephaly. They are also looking at possible links to molds and pesticides, while local residents are concerned that nuclear waste from a nearby nuclear power plant may be to blame.
Concerns about the cluster of birth defects in Washington state were first raised by a health-care provider in August 2012, after an excessive number of anencephaly births. Also known as neural tube defects, these problems often arise during the first month of pregnancy, which is a time when many women do not even know they are pregnant.
Neural tube defects are characterized by a hole in the spinal cord or brain because the neural tube does not close completely. This can result in defects that include spina bifida, and brain malformations that may result in parts of the brain missing or protruding from the skull.
The Washington Department of Health is reminding doctors about the importance of folic acid supplements for women of child-bearing age. Good folic acid levels are considered critical in the prevention of neural tube defects.