Observations on all births (23, 970) in Birmingham, 1947. VII. Effect of changing family size on infant mortality.

The object of this communication is to enquire to what extent the reduction in infant mortality during the 20th century may be attributed to changes in family size. This important question was referred to in Volume XIII (Pt II) of the 1911 Census of England and Wales (p. xlix). The census recorded for each married woman the total number of children born alive, and the number living and dead at the time of the Census. This made it possible to relate mortality to family size (but not to order of birth), and it was noted that: Whatever the ages of the parents and the duration of marriage the increase of mortality with number of births is very great, the rates being generally three to five times as high for the largest families as for the smallest.