This book investigates the biological and physiological mechanisms through which breastfeeding functions as a method of natural child spacing. Sheila Kippley, a recognized advocate for natural family planning, synthesizes anthropological data and physiological research to argue that breastfeeding is an evolutionary tool for regulating fertility. The text provides a framework for understanding the lactational amenorrhea method as a viable, non-contraceptive approach to family planning.

Experts in the field of natural family planning recognize this work as a foundational text for understanding the ecological aspects of breastfeeding. Readers frequently note the accessible yet informative nature of the prose, which bridges the gap between scientific theory and practical application for nursing mothers.