Factors related to duration of postpartum amenorrhoea among USA women with prolonged lactation
Heinig, M.J.; Nommsen-Rivers, L.A.; Peerson, J.M.; Dewey, K.G.
Journal of Biosocial Science 26(4): 517-527
1994
ISSN/ISBN: 0021-9320 PMID: 7983102 DOI: 10.1017/s0021932000021647Document Number: 332942
This analysis of factors affecting duration of postpartum amenorrhea (PPA) indicates that maternal anthropometric status is related even for healthy women. The analysis of 61 breast-feeding mothers and 42 formula-feeding mothers, who were in the study for at least six months, showed that the formula-feeding mothers had shorter mean and average durations of PPA (an average of 11.8 weeks versus 38.9 weeks for breast-feeding mothers). At 22 weeks, all formula-feeding mothers had resumed menstruation, while only 17% of breast-feeding mothers were menstruating. 75% of breast-feeding mothers did not resume menstruation after 26 weeks, and about 20% did not resume menstruation after 52 weeks. Timing of supplementation and nursing frequency were related to delays in menstruation. Longer durations of PPA were associated with later supplementation and no reduction in nursing frequency. A reduction of even one feed per day within the first six months among breast-feeding mothers was sufficient to reduce PPA. Formula-feeding mothers who maintained at least one breast feeding per day for a week had longer PPA by eight weeks. Hazard analysis revealed that parity was positively associated with and maternal body mass index (BMI) was negatively associated with duration of PPA at three months postpartum. When resumption of menstruation occurred at six months and after, the important positively-related factors were parity, pregnancy weight gain, number of night feeds and milk volume at six months; maternal age and BMI at six months were negatively related. Time changes amounted to an increase in PPA duration of five weeks for multiparity mothers, 0.5 weeks for each kg of weight gain during pregnancy, five weeks for each night feed at six months, and three weeks for each 100 g of milk produced. PPA was reduced by two weeks for every unit increase of BMI at six months. Milk volume and feeding frequency were unrelated at three months. More research is needed on the influence of maternal body fat on hormonal levels in lactating women in order to understand the impact of maternal body mass on amenorrhea.