Factors influencing the timing of initial breastfeeding in 954 out-of-hospital births

Hormonal correlates for the initiation of breast-feeding in Bangladeshi women

Hormonal changes that occur before or during parturition are known to trigger early postpartum maternal behaviors in many mammals. In humans, little evidence has been found for hormonal mediation of early postpartum maternal behavior. In this paper, we investigate associations between fetoplacental hormone concentrations in late pregnancy on the time from parturition to initiation of breast-feeding. A sample of 91 pregnant rural Bangladeshi women, enrolled in a 9-month prospective study, provided twice-weekly urine specimens and structured interviews. The subjects provided self-reports of time from parturition to initiation of breast-feeding. Specimens were assayed for urinary concentrations of human chorionic gonadotropin (hCG), pregnanediol-3alpha-glucuronide (PdG, a metabolite of progesterone), and urinary estrone conjugates (E1C). Parametric hazards analysis was used to investigate the effects of hCG, PdG, and E1C concentrations and other covariates (mother's age, parity, and child's sex) on the duration from parturition to breast-feeding. Mother's age, parity, the child's sex, hCG, and PdG showed no association with the onset of breast-feeding. Urinary E1C was significantly associated with time to initiation of breast-feeding, explaining about 4% of the variation in the behavior. The relationship was positive so that higher prepartum concentrations of EIC were associated with later times to initiation of breast-feeding. The direction of this relationship is opposite that found for many other species of mammals but is consistent with some recent findings in primates.

Patterns for the initiation of breastfeeding in humans

Establishment of lactation has important biological and emotional health consequences for the newborn. Even so, substantial variation within a culture and among different cultures is seen in the onset of breastfeeding. Parametric mixture models are used to explore this variation and to uncover general human patterns for the initiation of breastfeeding. The model components reflect two hypothesized patterns of behavior. The first component is a "natural" pattern of breastfeeding that reflects, to some extent, a general mammalian behavior. The second component arises through culturally mediated behaviors that affect the initiation of breastfeeding. The model was fit by maximum likelihood to interval- and right-censored observations on 26220 mother-infant pairs collected from 25 previously published studies of breastfeeding behavior. Both model components were clearly statistically identified. Effects of cultural and geographic covariates were found to have significant effects on all components of the model. Although there is clear evidence for two distinct patterns of behavior in the initiation of breastfeeding, the results suggest that learned behaviors play an important role in mediating even "natural" breastfeeding behavior.