James W H
Dev Med Child Neurol. 1980 Oct;22(5):618-22. doi: 10.1111/j.1469-8749.1980.tb04375.x.
Anencephalic infants born to women who are very prone to bear them do not have a sex ratio appreciably different from that of other anencephalic births. Moreover, the sexes of affected cases in sibships containing exactly two anencephalic births seem to be distributed approximately binomially. Bearing in mind the correlation between prevalence at birth and sex ratio in anencephaly, these findings suggest that an environmental teratogen attacks the fetuses of women who are already (perhaps genetically) disposed to bear anencephalic infants.
极易生出无脑儿的女性所生的无脑儿，其性别比例与其他无脑儿出生情况相比并无明显差异。此外，在恰好有两例无脑儿出生的同胞胎次中，患病病例的性别分布似乎近似二项分布。考虑到无脑儿出生时的患病率与性别比例之间的相关性，这些发现表明，一种环境致畸因素会攻击那些已经（或许是基因上）倾向于生出无脑儿的女性的胎儿。
