We conducted a prospective study of the associations between several biologic and surgical breast factors and the onset of lactation in 319 healthy, motivated, primiparous women who were breastfeeding term, healthy, appropriate for gestational age or large for gestational age infants. During the last trimester of pregnancy subjects' breasts were examined for surgical incisions, size, symmetry, and nipple protuberance, and women estimated their prenatal breast enlargement. At two visits in the first two weeks postpartum, infants were weighted naked, and mothers reported the magnitude of postpartum breast engorgement when their milk came in. Breastfeeding was evaluated at each visit, and interventions were recommended for problems, with emphasis on maximizing milk yield. Lactation was deemed sufficient when an exclusively breastfed infant achieved an average weight gain of 28.5 g or more per day between the two visits. Infants gaining less than 28.5 g per day with breast milk exclusively, and those requiring formula supplement returned for a third visit at or before 21 days of age, when final lactation outcome was assessed based on weight gain between the second and third visits. Within three weeks postpartum 85 percent of the mothers achieved sufficient lactation, whereas 15 percent had persistent milk insufficiency despite intensive intervention. Of the study population, 6.9 percent had undergone previous breast surgery. Women with periareolar breast incisions were nearly 5 times more likely to have lactation insufficiency than were those without surgery (relative risk [RR] = 4.55; 95 percent confidence interval [CI] = 2.21-9.43; P less than 0.001). Insufficient lactation was significantly associated with minimal prenatal breast enlargement (P less than 0.02) and minimal postpartum breast engorgement when milk came in (P less than 0.001). Although not statistically significant, women with inverted nipples were more likely to have lactation insufficiency compared with those with normal nipples (RR = 2.94; 95% CI 1.05-8.20; P = .07). The findings from this study indicate that certain biologic and surgical breast variables are associated with lactation insufficiency.
A higher incidence of preterm birth (PTB) and premature rupture of membranes (PROM) has been observed among women delivering male newborns compared with female newborns in different populations. Some authors have speculated that this higher incidence of PTB may be related to the relatively greater weight at lower gestational age of male newborns compared with female newborns. Others have suggested that the greater incidence of PTB and PROM is caused by an increased vulnerability to infection in women carrying males. To understand possible pathogenic factors leading to PTB further, we examined the association between PTB and infant gender in a cohort of North American women. In addition, incidences of PROM, chorioamnionitis, and postpartum endometritis were analyzed for women delivering males versus females. Overall, males were more likely than females to deliver at 33 to 36 weeks' gestation (OR = 1.21; 95% CI: 1.02-1.42). This increase in PTB among males was not accompanied by an increased number of males with low birthweight; rather, males were less likely than females to weigh between 2000 and 2499 gm (OR = 0.71; 95% CI: 0.60-0.84). The difference in PTB by gender could not be explained by an increased occurrence of PROM, chorioamnionitis, endometritis, or other infection-linked processes. Our findings suggest that shorter gestation in males in this population may be related to their relatively increased size and birthweight. Male gender-associated factors that predispose to infection-mediated preterm birth may play greater roles in populations at higher risk for reproductive tract infection during pregnancy.
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