Breast-feeding and post partum amenorrhea in Central Africa.
The long duration of postpartum amenorrhea in rural central Africa contributes to a natural inter-birth spacing of 33 to 39 months. This study examines the postpartum (0 to 24 months) nursing woman's secretory profile of different hormones involved in the reproductive process, particulary prolactin. Controls chosen from the same population group (from a rural area and from the city of Bukavu on the highlands of Zaire) consisted of non-nursing non-pregnant women and adult men of the same age group. Serum follicular stimulating hormone (FSH), luteinizing hormone (LH), serum prolactin and serum estradiol were measured by various radioimmunoassay techniques. The findings show that lactating mothers remain hyperprolactinaemic during the 1st 18 postpartum months. Hyperprolactinemia is maintained by breastfeeding and is higher when the feedngs are more numerous and/or closer in time. Prolactin levels are significantly higher in amenorrheic mothers than in menstruating ones, with the difference being much less marked during the 2nd postpartum year than during the 1st. It was suggested that all women are amenorrheic above a certain threshold of serum prolactin. Serum prolactin levels declined significantly in the city of Bukavu but not in the rural area. Only 15% of nursing mothers resumed their menses after 12 postpartum months in the rural area; the corresponding figure in the city is close to 50%. The relationship between lactation hyperprolactinemia and postpartum amenorrhea is not only based on valid statistical associations, but also in similarities between the endocrine pattern of physiological hyperprolactinemia and that seen in pharmacological hyperprolactinemia.