An analysis of reproductive patterns in an American isolate

Abstract

Abstract The reproductive patterns of an American Anabaptist group with high birth rates and which apparently does not practise deliberate limitation of family size are characterized by short intervals between successive births. The mean intervals tend to increase in length with maternal age (or rising birth order), but they are under two years for the first 10 births. In agreement with conclusions suggested by theoretical models, the data indicate that the high birth rates observed here are due primarily to a relatively short duration of the post-partum period of reduced fecundability. It has been reported that these women customarily nurse their babies until a new pregnancy supervenes. If this is accurate, questions arise whether lactation affects ovulation less in this population than in others, or perhaps whether the supplemental feeding is introduced sooner and this stimulates earlier resumption of ovulation. Since this group enjoys high levels of health and nutrition, it would be of great interest t...