LACTATION, NUTRITION, AND POSTPARTUM AMENORRHEA IN LOWLAND PAPUA-NEW-GUINEA

Prolonged on-demand breast feeding is known to delay the resumption of postpartum ovarian cyclicity. At present, however, little is known ab out the factors that influence the effectiveness of breast feeding as a natural contraceptive. Here, I examine the effects of maternal nutri tional status on the duration of postpartum amenorrhea in two socioeco nomic groups of Au forager-horticulturalists of lowland Papua New Guin ea. Although women in both groups continue to breast-feed their offspr ing for approximately three and one-half years, well-nourished wage-ea rning Au women experience their first postpartum menses just over one year earlier (median = 12.5 months) than their more poorly nourished t raditional counterparts (median = 26.6 months). Probit analyses are us ed to demonstrate that, even after controlling for time since delivery , maternal age, parity, and supplementation of infants' diets, the dur ation of postpartum amenorrhea is significantly (p < 0.05) negatively associated with indexes of maternal fat mass. No association between i ndexes of maternal lean body mass and the duration of postpartum ameno rrhea were found. The results of this study suggest that components of maternal nutritional status, in particular, adiposity, play an import ant role in influencing fecundity in human populations.