140210-birth-defect-cluster-main_fd0110563863025f2c556f2fec9fbe0b.nbcnews-fp-720-440A mysterious cluster of severe birth defects in rural Washington state is confounding health experts, who say they can find no cause, even as reports of new cases continue to climb.  Federal and state officials won’t say how many women in a three-county area near Yakima, Wash., have had babies with anencephaly, a heart-breaking condition in which they’re born missing parts of the brain or skull. And they admit they haven’t interviewed any of the women in question, or told the mothers there’s a potentially widespread problem. But as of January 2013, officials with the Washington state health department and the Centers for Disease Control and Prevention had counted nearly two dozen cases in three years, a rate four times the national average. Since then, one local genetic counselor, Susie Ball of the Central Washington Genetics Program at Yakima Valley Memorial Hospital, says she has reported “eight or nine” additional cases of anencephaly and spina bifida, another birth defect in which the neural tube, which forms the brain and spine, fails to close properly. “It does strike me as a lot,” says Ball. And at least one Yakima mother whose baby is part of the cluster says no one told her there was a problem at all. “I had no idea,” said Andrea Jackman, 30, whose blue-eyed daughter, Olivia, was born in September with the most severe form of spina bifida. “I honestly was really surprised that nobody had said anything. If my doctor hadn’t wanted us to see the geneticist, I wouldn’t have known.” More