Influence of breast-feeding pattern on pituitary-ovarian axis of women in an industrialized community.

A longitudinal study of 48 postpartum women showed that during the first 6 months the daily frequency of infant feedings remained between six and seven. The lower threshold of the ratio breast-feedings/supplementary feedings that sustained both hyperprolactinemia and anovulation was 4.5/1. The duration and the 24-hour distribution, but not the intensity, of breast-feedings were significantly altered during prolonged lactation and when supplementary feeding was used. However, neither differences in the levels of prolactin (PRL) no gonadal status could be correlated with qualitative differences in the breast-feeding pattern. Postpartum maternal body weight was not related to serum PRL, gonadotropins, or resumption of ovulation, but mothers who smoked cigarettes had significantly lower serum levels of PRL during the third and fourth months, and weaned their babies earlier, than did mothers who were nonsmokers. Our data showed that minor quantitative differences in the feeding pattern have a significant impact on the pituitary-gonadal axis, and that the decline in the levels of PRL during continued lactation is due mainly to a decreased frequency of breast-feeding but may be due also to a shorter duration and more heterogeneous 24-hour distribution of nursings but not to a reduced intensity of sucking.