We analyze trends in the use of traditional and modern means of contraception and their effect on fertility over the last decades. The contraceptive effect of breastfeeding remains essential to controlling fertility in many developing regions, but the extent to which this inhibiting effect on ovarian activity is sensitive to ecological conditions, notably maternal energetic status, has remained controversial. We assess the relationship between breastfeeding duration and the absence of menstruation following a birth (i.e., postpartum amenorrhea) in more than 84 low- and middle-income countries since 1975. The data reveal a sharp weakening of the breastfeeding–postpartum amenorrhea relationship globally over the time. Progress in human development and urbanization lead to a weaker effect of breastfeeding on extending postpartum amenorrhea. These findings indicate that the relationship is partly mediated by external factors that probably include negative maternal energy balance. Prolonged breastfeeding significantly helps control fertility only under harsh environmental conditions. It is thus urgent to develop family planning interventions in the postpartum period. A follow-up research focuses on the spread of modern means of contraception among developing countries, with a special interest in how socioeconomic development and crises affect this process of behavioral diffusion.
Relationship between duration of breastfeeding and post-partum amenorrhea in 85 low- and middle-income countries, 1975-2019:
Source: Todd, N., M. Lerch (2021): Socioeconomic development predicts a weaker conctraceptive effect of breastfeeding, in: Proceedings of the National Academy of Sciences of the United States of America (PNAS), 118 (29) e2025348118