ABSTRACT
Numerous studies of different aspects of the hypothesized fertility effects of body weight, fatness, and nutrition level have been published. Detailed reviews of the evidence conclude that bodyweight or fatness are not important determinants of postpartum amenorrhea or birth intervals. Instead, the duration, pattern, and intensity of breastfeeding are the principal determinants of postpartum amenorrhea. During the 1963-1973 period fertility was less than 5 births per woman, an unusually low level. The principal cause of the rise in fertility between the period 1963-1973 and the late seventies is the shortening of postpartum amenorrhea. One of the studies that is most damaging to the critical weight hypothesis as applied to the postpartum interval has been conducted in rural Guatemala.
