RESUMO
Peripartal maternal apprehension and anxiety are associated with abnormal labour, dystocia and higher rates of fetal and maternal morbidity. Since colostral beta-endorphin (beta-EP) concentrations are twofold higher than circulating levels, we hypothesised that substantial maternal emotional distress in puerperium might induce consistent changes in colostral beta endorphin galactopoiesis. To test this hypothesis, we assessed the effects of postpartum maternal anxiety (State-Trait Anxiety Inventory-Y form, Spielberger CD, Palo Alto, CA, USA, 1983) on colostral milk beta-EP levels (beta-endorphin 125I RIA, INCSTAR Corporation-Stillwater, Minnesota, USA) in a population of healthy lactating mothers, on the fourth postpartum discharge day, 14 after at term vaginal delivery, 14 after premature (> or = 34 <37 gestational weeks) vaginal delivery, and 14 after elective cesarean section. The colostral milk beta-EP concentrations of mothers who vaginally delivered at term or prematurely were significantly higher on the fourth postpartum day (6.0+/-0.5 and 6.6+/-0.7 vs. 4.3+/-0.4 pmol/l, respectively; P <0.05) than colostral levels of mothers who underwent caesarean section. At the same time, while trait anxiety levels (T, age corrected values) were unaffected by route and mode of delivery, in mothers presenting increased colostral milk beta-EP galactopoiesis after vaginal delivery there was a statistically significant negative correlation (r-0.40; P <0.03) between colostral milk beta-EP concentrations and trait anxiety levels. These data indicate that the labour pain and the vaginal delivery process play a central role in increasing colostral opioid availability for the breastfed neonate; peripartal maternal anxiety is a negative psychobiological determinant in opioid galactopoiesis, and possibly in the postnatal development of several related biological functions of growing infants.
RESUMO
BACKGROUND: The source and regulatory mechanisms that elevate beta-endorphin (beta-EP) approximately twofold higher than circulating plasma levels in the colostrum of lactating mothers are still unknown, and no studies have examined beta-EP availability previously during maturation phases of human milk. Therefore, the aim of this study was to determine whether concentrations of beta-EP vary over time between colostrum, transitional, and mature breast-milk and to evaluate whether this depends on the method of delivery. METHODS: Mothers of healthy full-term and pre-term newborn infants who planned to breast-feed their newborn infants were considered for this study. They were consecutively recruited in one of 3 groups of 14, according to delivery method: group 1, vaginal delivery at term (gestational age 40.2 +/- 0.3 weeks; birth weight, 3.48 +/- 0.09 kg); group 2, preterm vaginal delivery (gestational age, 35.6 +/- 0.3 weeks; birth weight, 2.49 +/- 0.08 kg); and group 3, at-term elective cesarean section (gestational age, 39.0 +/- 0.3 weeks; birth weight, 3.32 +/- 0.14 kg). Three consecutive breast milk samples were obtained on the fourth day after birth, before each mother's discharge, and thereafter on the 10th and 30th postpartum days, close to expression of the colostrum, transitional, and mature milk production phases, respectively, to test beta-EP concentrations (beta-Endorphin 125I RIA; INCSTAR Corporation, Stillwater, MN). Data are presented as mean +/- standard deviation. Statistical comparison of beta-EP concentration among the three lactating mother groups was performed using the Kruskal-Wallis nonparametric test. In addition, to test the hypothesis of a trend toward smaller values with time of beta-EP, the authors computed within each mother group a P value per trend (Kruskal-Wallis test) of beta-EP concentration averages on the 4th, 10th, and 30th days, respectively. Student's t test for independent samples was used for the analysis of the other data. The 0.05 significance level was used in the statistical analysis. All computations were made by computer. RESULTS: Colostrum beta-EP concentrations on the fourth postpartum day of group 1 and group 2 mothers who were delivered of a neonate vaginally, at term, or prematurely were significantly higher (P < 0.01) than colostrum levels of group 3 mothers who underwent cesarean section. Group 2 mothers who were delivered of a neonate vaginally and prematurely presented the highest beta-EP concentrations (P < 0.05), lasting until the transitional milk phase (10th day). No significant differences were found across all 3 groups of lactating mothers in mature milk (30th day) beta-EP concentrations. In addition, the beta-EP trend toward smaller values with time within each of the three groups on days 4, 10, and 30 was statistically significant (P < 0.01 per trend). CONCLUSIONS: It is hypothesized that elevated beta-EP concentrations in colostrum and transitional milk of mothers who were vaginally delivered of infants may contribute to postnatal fetal adaptation, to overcoming birth stress of natural labor and delivery, and at the same time to the postnatal development of several related biologic functions of breast-fed infants.
Assuntos
Colostro/química , Trabalho de Parto/fisiologia , Lactação/fisiologia , Leite Humano/química , beta-Endorfina/análise , Adulto , Cesárea , Feminino , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Estudos Longitudinais , Dor , GravidezRESUMO
beta-Endorphin (beta-EP) levels of colostral milk are approximately two-fold higher than in plasma of lactating women, in who concentrations peak at term, after the first and second stages of labor. We investigated the effect of labor pain and vaginal parturition on colostral beta-EP concentrations (beta-endorphin (125)I RIA, Incstar Corp., Stillwater, Minn., USA) of at-term nursing mother, in comparison to those having undergone elective cesarean section. Our results show that colostral milk beta-EP concentrations of mothers who delivered vaginally are significantly higher on the 4th postpartum day (6.0 +/- 0.5 vs. 4.3 +/- 0.4 pmol/l, respectively; p < 0.01) than colostral levels of mothers who underwent cesarean section. These data indicate the important influence of the labor process on the colostral opioid galactopoiesis. It is suggested that labor and parturition pain may increase colostral milk beta-EP concentrations of lactating mothers in order to help the newborn overcome the stressful perinatal events of natural labor and delivery.