Lactation and Pregnancy: A Hypothesis

Abstract

After a brief review of existing studies on the subject an hypothesis concerning the relationship which is known to exist but remains to be clarified between lactation and anovulation is presented. This relationship is a common subject of folklore and folk medicine but is yet to be dealt with by science. It is noted that the majority of scientific studies concerning lactation were performed in Western developed countries where cultural mores result in faster weaning and earlier introduction of supplementary foods. However in many countries and areas of the world lactation is continued for 4 years in nearly 100% of cases. Studies have also noted a relationship between onset of postpartum menstruation and mothers socioeconomic levels with lower-economic-scale women menstruating postpartum later than women from higher socioeconomic classes. In view of this evidence it is suggested that the process of lactation as it occurs among peasant and undeveloped populations is generally not comparable to that which occurs in highly industrialized cultures (U.S. or Europe). In the former group lactation tends to be a long-term intensive process which includes frequent nonscheduled stimulations of the breast which may inhibit ovulation until later when the child is weaned to other foods. In comparison developed nations with greater access to pediatric care begin supplementing breastfeeding with foods at earlier ages thereby decreasing the frequency and duration of feedings. Such children are generally weaned by age 1 year and these practices seem to lead to early resumption of ovarian function. This hypothesis is said to account for the fact that in modern studies the relationship between sterility and lactation has been obscured.