Comparative study of nursing mothers in Africa (Zaire) and in Europe (Sweden): breastfeeding behaviour, nutritional status, lactational hyperprolactinaemia and status of the menstrual cycle.

A total of 1036 nursing mothers were investigated for their nursing behaviour, status of nutrition and menstrual cycle, serum prolactin and progesterone; 61 in Sweden, 457 in an urban area of Zaïre (Bukavu, Kivu) and 518 in a rural area of the same region (Kabare, Kivu). Lactational hyperprolactinaemia is influenced by the frequency but not by the duration of suckling. The return of luteinization of follicles, but not that of menstrual bleeding, was inversely related to the degree of lactational hyperprolactinaemia. Significant luteinization took place in only some 10% of the mothers during the first three months of lactation in Sweden and within the first year in Zaïre. In these mothers with luteinized follicles the average progesterone was only slightly above 1.0 ng/ml indicating poor luteinization. Lactational hyperprolactinaemia, the return of menstruation and luteinization during lactation were not related to the nutritional status as evaluated by the body weight indices and serum albumin. However, suckling and hyperprolactinaemia do not appear to be the only factors involved in the control of fertility during lactation. When serum prolactin levels were equally low, i.e. below 500 microU/ml, twice the number of lactating mothers with signs of luteinization were found in the urban than in the rural population of Zaïre.