 Even though “scientifically rigorous studies of causes of human birth defects generally require evaluation of hundreds of birth defects or more", the CDPH's objectives were limited and largely focused on evaluating risk factors because of the fewer than dozen cases of birth defects in Kettleman City.The CDPH investigated a total of 11 eligible children born with major, structural birth defects between 2007 and March 31, 2010 to mothers who had lived in the Kettleman City area during their pregnancies.Through a mixed-methods approach consisting of interviews and supplementary medical history reports the CDPH did not find a specific cause or environmental exposure among the mother that would explain the increase in the number of children born with birth defects.