Elwood J M, Elwood J H
Int J Epidemiol. 1982 Jun;11(2):132-7. doi: 10.1093/ije/11.2.132.
Information from series of cases of anencephalus and corresponding random samples of all livebirths showed that the prevalence rate at birth per 1000 livebirths for anencephalus was 4.02 in Belfast (from 1957 to 1969), compared to 1.36 in mothers of Scots-Irish origin resident in 14 selected Canadian cities (from 1950 to 1969). For each of these two populations, anencephalus was associated with the number of previous livebirths, stillbirths, and child deaths. However, these maternal factors did not account for any appreciable portion of the difference in prevalence rates between the two populations, showing that a different set of factors must cause the international difference in rates.
无脑儿系列病例以及所有活产儿相应随机样本的信息表明，在贝尔法斯特（1957年至1969年），无脑儿的出生患病率为每1000例活产中有4.02例，而居住在加拿大14个选定城市的苏格兰 - 爱尔兰裔母亲（1950年至1969年）中该患病率为1.36例。对于这两个人群中的每一个，无脑儿都与既往活产、死产和儿童死亡的数量有关。然而，这些母亲因素并未解释两个人群患病率差异的任何可观部分，这表明一组不同的因素必定导致了国际间的患病率差异。
