The negative effect of breastfeeding on fertility may be more sensitive to environmental conditions than previously thought, a study suggests. The postpartum suppression of ovarian function by breastfeeding helps control population growth in many developing countries. In the early 1980s, John Bongaarts and Robert Potter found a tight link between the durations of breastfeeding and postpartum amenorrhea, or lack of menstruation, and proposed a mathematical formula based on this finding. Nicolas Todd and Mathias Lerch tested whether this formula still holds, particularly in low-income and middle-income countries (LMICs), which have experienced rapid economic growth and health improvements over the past four decades. The authors analyzed data from 301 fertility and health surveys administered in 84 LMICS between 1975 and 2019. Overall, the Bongaarts-Potter function was not sufficiently accurate, overestimating the duration of postpartum amenorrhea by an average of 1.6 months. Moreover, characteristics such as access to electricity and easy access to water were associated with a weakened relationship between breastfeeding and postpartum amenorrhea. Taken together, the findings suggest that improved living standards and related factors, such as reduced physical labor and increased food intake, may have reduced the contraceptive effect of breastfeeding in LMICs in recent decades, according to the authors.
Article #20-25348: "Socioeconomic development predicts a weaker contraceptive effect of breastfeeding," by Nicolas Todd and Mathias Lerch.
MEDIA CONTACT: Nicolas Todd, Max Planck Institute for Demographic Research, Rostock, GERMANY; email: email@example.com
Proceedings of the National Academy of Sciences