Health officials continue to look into several cases of the rare birth defect anencephaly in Benton, Franklin and Yakima counties.
A study led by the state Department of Health found no clear cause for the high number of cases. In all, 23 cases were found in the three counties from January 2010 through January 2013, or about 8.4 per 10,000 live births -- four times the national rate.
Officials have kept gathering data, and an update that could shed more light on the issue is expected in a few months.
Babies with anencephaly, a neural tube defect, are born without parts of their brain and skull, and most die shortly after birth, according to the Centers for Disease Control and Prevention.
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The state Department of Health announced the results of the initial study last summer and stories appeared in the Tri-City Herald and other media, but the matter has seen renewed public attention after a national news report last week on the same data.
NBC News profiled a Yakima-area mother whose daughter was born with a form of spina bifida, another neural tube defect, and also spoke with some officials and experts. A genetic counselor in Yakima said she's reported additional cases of anencephaly and spina bifida since January 2013.
Anencephaly and spina bifida can happen when women don't get enough folic acid before and early in their pregnancy. At least 400 micrograms is recommended a day.
Other factors can include some medications, diabetes, obesity in pre-pregnancy and previously having a child with a neural tube defect, the state health department said.
Women who rely on a private well for drinking water also should have the well tested at least once a year for nitrate and bacteria, and switch to a different source if the levels exceed standards, the department said.
Babies born to Hispanic women have a greater risk for anencephaly, although the reasons aren't well understood, according to the CDC.
The initial study in Benton, Franklin and Yakima counties involved reviewing medical records and comparing them to more than 100 control subjects. A county-by-county breakdown of the 23 anencephaly cases wasn't available.
Three cases of spina bifida also were found. That rate of 1.3 per 10,000 live births was lower than the national rate.
Dr. Amy Person, health officer of the Benton-Franklin Health District, said women should follow all the standard recommendations before and during pregnancy, including getting enough folic acid.
"Sometimes you'll see a random increase, but then the numbers go away and there's no cluster anymore. That's why we're continuing to follow, to see if there is a trend" or if the spike was coincidental, Person said.
"We are continuing to follow this to make sure we are keeping the community as healthy as always," she told the Herald.
-- Sara Schilling: 582-1529; firstname.lastname@example.org; Twitter: @saraTCHerald