Effects of suckling on hypothalamic-pituitary-adrenal axis responses to psychosocial stress in postpartum lactating women

A pilot study of maternal and term infant outcomes associated with ultrathin nipple shield use

OBJECTIVE

To examine maternal satisfaction with nipple shield use and maternal and infant physiological outcomes of breastfeeding with and without nipple shields.

DESIGN

A descriptive study using a structured telephone survey to examine maternal satisfaction of nipple shield use and a within-subject design to compare maternal and infant physiological outcomes for a subset of mother-infant dyads.

SETTING

Breastfeeding sessions were conducted in Pacific Northwest hospitals.

PARTICIPANTS

32 lactating women with experience using nipple shields; a subset of 5 maternal-infant dyads participated in the physiological part of the study.

MAIN OUTCOME MEASURES

Maternal response to survey explored maternal satisfaction with nipple shield use. To examine maternal and infant physiological outcomes, two measures were used: infant test weighing to evaluate breast milk intake and maternal prolactin and cortisol levels to evaluate breast milk production.

RESULTS

Maternal survey response indicated that use of nipple shields may prevent premature breastfeeding termination. Physiological results demonstrated no significant difference in maternal hormonal levels and infant breast milk intake for breastfeeding sessions with and without nipple shields.

CONCLUSION

Use of nipple shields may be considered in face of potential abandonment of breastfeeding.

Learning during motherhood: A resistance to stress

Hormonal and emotional responses to stress are diminished during pregnancy and the postpartum period. However, the effects of stress on learning during these stages of the female life span have not been examined. In previous studies, we have reported that exposure to an acute stressful event reduces classical eyeblink conditioning 24 h later in adult virgin female rats that are experiencing an ovarian cycle. Here we show that conditioning during late pregnancy was similarly reduced by stressful experience. However, conditioning in postpartum females was unaffected by stressor exposure. The resistance to stress during the postpartum period was evident as early as 2 days after parturition and persisted until the late postpartum period, just prior to weaning. Postpartum conditioning was unresponsive to numerous types of stressors, including brief inescapable tailshocks, swim stress, and exposure to a male intruder. The resistance to stress appears to be dependent on the presence of the offspring, because the impairment in conditioning returned when postpartum females were separated from their pups. Moreover, the resistance to stress occurred in virgin females that behaved maternally after being exposed to young pups for several days. Together, these data suggest that the presence of offspring and the nurturing and care-giving activities that they elicit protect females from the adverse effect of stress on processes involved in learning and memory.

The effects of sex and hormonal status on the physiological response to acute psychosocial stress

Whether one is male or female is one of the most important determinants of human health. While males are more susceptible to cardiovascular and infectious disease, they are outnumbered by women for many autoimmune disorders, fibromyalgia and chronic pain. Recently, individual differences in the physiological response to stress have emerged as a potentially important risk factor for these disorders. This raises the possibility that sex differences in prevalence of disease could at least in part be explained by sex differences in the nature of the physiological response to stress. In a psychophysiological laboratory, the autonomic nervous system response can be provoked by many different stressors including physical, mental and psychosocial tasks, while the hypothalamic-pituitary-adrenal axis (HPAA) response seems to be more specific to a psychosocial challenge incorporating ego involvement. The responses of both systems to different psychosocial challenges have been subject to extensive research, although in respect of sex differences the HPAA response has probably been more systematically studied. In this review, we focus on sex differences in HPAA and autonomic nervous system responses to acute psychosocial stress. Although some differences are dependent on the stressor used, the responses of both systems show marked and consistent differences according to sex, with the phase of the menstrual cycle, menopausal status and pregnancy having marked effects. Between puberty and menopause, adult women usually show lower HPAA and autonomic responses than men of same age. However, the HPAA response is higher in the luteal phase, when for example post stress free cortisol levels approach those of men. After menopause, there is an increase in sympathoadrenal responsiveness, which is attenuated during oral hormone replacement therapy, with most evidence suggesting that HPAA activity shows the same trends. Interestingly, pregnancy is associated with an attenuated response of the sympathoadrenal and HPAA systems at least as assessed by biochemical stimulation. It is likely that these sex differences in autonomic function are a result of estrogen exposure which attenuates sympathoadrenal responsiveness. The HPAA is however somewhat more complex and evidence now suggests the influence of other modifiers such as arginine vasopressin (AVP) and the regulation of circulating cortisol bioavailability by corticosteroid-binding globulin (CBG). The pronounced and multi-faceted sex differences in stress responsiveness suggest that they are a product of a strong evolutionary pressure. We hypothesise that this has to a great deal been driven by the need to protect the fetus from the adverse effects of maternal stress responses, in particular excess glucocorticoid exposure. Studying this hypothesis may have a fundamental impact on our understanding about how adult health is set during early life and how adult disease could be prevented in men and women.

Early infant feeding decisions in low-income Latinas

Breastfeeding rates remain low, especially among low-income minority women. The objective of this qualitative study was to assess barriers to breastfeeding and reasons for combination feeding among low-income Latina women and their families. Meetings were held with key informants to inform the sampling plan and develop questions for focus groups. Data were collected from eight qualitative focus groups with primiparous mothers postpartum, mothers breastfeeding at 4 to 6 months, mothers formula feeding at 4 to 6 months, grandmothers and fathers, and 29 individual interviews with formula- and combination-feeding mothers. Transcripts of focus groups and interviews were content coded and analyzed for thematic domains and then compared for concurrence and differences. Four main domains with 15 categories were identified: (a) Best of both: Mothers desire to ensure their babies get both the healthy aspects of breast milk and "vitamins" in formula. (b) Breastfeeding can be a struggle: Breastfeeding is natural but can be painful, embarrassing, and associated with breast changes and diet restrictions. (c) Not in Mother's Control: Mothers want to breastfeed, but things happen that cause them to discontinue breastfeeding. (d) Family and cultural beliefs: Relatives give messages about supplementation for babies who are crying or not chubby. Negative emotions are to be avoided so as to not affect mother's milk. Those counseling Latina mothers about infant feeding should discourage and/or limit early supplementation with formula, discuss the myth of "best of both," understand the fatalism involved in problem-solving breastfeeding issues, and enlist the altruism embedded in the family unit for support of the mother-infant pair.

Differences between exclusive breastfeeders, formula-feeders, and controls: a study of stress, mood, and endocrine variables

The purpose of this study was to examine relationships among lactational status, naturalistic stress, mood, and levels of serum cortisol and prolactin and plasma adrenocorticotropic hormone (ACTH). Eighty-four exclusively breastfeeding, 99 exclusively formula-feeding, and 33 nonpostpartum healthy control women were studied. The postpartum mothers were studied cross-sectionally once between 4 and 6 weeks after the birth. Stress was measured using the Perceived Stress Scale, the Tennessee Postpartum Stress Scale, and the Inventory of Small Life Events. Mood was measured using the Profile of Mood States. Serum prolactin, plasma ACTH, and serum cortisol levels were measured by commercial ELISA (enzyme-linked immunosorbent assay) kits. Results indicate that breastfeeding mothers had more positive moods, reported more positive events, and perceived less stress than formula-feeders. Reports of stressful life events were generally equivalent in the two groups. Serum prolactin was inversely related to stress and mood in formula-feeders. When breast and formula-feeders were compared to controls, they had higher serum cortisol, lower stress, and lower anxiety. Breastfeeders had lower perceived stress than controls. Breastfeeders had lower depression and anger and more positive life events reported than formula-feeders. However, there were few correlations among stress, mood, and the hormones in postpartum mothers, and those only in formula-feeders, whereas strong relationships were found between serum ACTH and a number of stress and mood variables in controls. Postpartum mothers reported a range of stress and negative moods at 4 to 6 weeks, and in formula-feeders, serum prolactin was related to some of the stress and mood variables. Breastfeeding appears to be somewhat protective of negative moods and stress.

Psychological determinants of the cortisol stress response: the role of anticipatory cognitive appraisal

Psychosocial stress is a potent activator of the hypothalamus-pituitary-adrenal (HPA) axis. While the physiological mechanisms of HPA axis responses to stress as well as its short and long-term consequences have been extensively examined, less is known why someone elicits an acute neuroendocrine stress response, i.e. what are the psychological processes involved and how are they related to the acute neuroendocrine stress response. To examine this question, a questionnaire to assess anticipatory cognitive appraisal processes was developed and administered to 81 male healthy subjects in a standardized psychosocial stress situation (Trier social stress test). Cortisol stress responses were assessed with repeated measurement of salivary free cortisol. Hierarchical regression analyses show that anticipatory cognitive appraisal, in contrast to general personality factors and retrospective stress appraisal is an important determinant of the cortisol stress response, explaining up to 35% of the variance of the salivary cortisol response. The reported results emphasize the importance of psychological stress processing for the understanding of psychobiological stress responses. Since stress and its biological consequences have been shown to be associated with the onset and the maintenance of somatic illnesses and psychiatric disorders, psychological processes are prime targets for prevention and intervention.

Measuring stress responses in postpartum mothers: perspectives from studies in human and animal populations

Reduced hypothalamic-pituitary-adrenal (HPA) responses to stress during the last week of pregnancy and lactation have been consistently observed in rat studies. Several contributing factors have been proposed for this phenomenon in lactation, including the suckling stimulus from the pups, hormones (oxytocin and prolactin) and opioids, a decrease in the ability of noradrenaline to potentiate hypothalamic responses and changes in pituitary responsiveness to ACTH secretagogues (AVP and CRF). In contrast to this vast literature using the rat model, only few studies have addressed this issue in the human population. The consensus is that women engaging in breastfeeding activities exhibit reduced anxiety, although the reductions in neuroendocrine and autonomic responses to stressors are variable, in part because of the different nature of the stressors used. Further work is required to investigate how additional factors, such as maternal parity or emotional salience of the stressor can affect stress responsiveness in postpartum women. Here, we review first the findings regarding stress responsiveness during lactation in both rat and human studies, and then discuss potential research avenues and methodological issues that could be the lead to future research protocols in human subjects. Knowing the reciprocal relationship in the mother-infant dyad, it is clear that investigation of the mechanisms regulating stress responses and mental health in postpartum mothers can only be beneficial to the development of the infant.

Grief, Anxiety, Stillbirth, and Perinatal Problems: Healing With Kangaroo Care

A young, anxious mother's first pregnancy was eclamptic, her placenta was underperfused, and her son was stillborn. She carried grief, guilt, anxiety, and hypervigilance into her next preeclamptic pregnancy, birth (of her small-for-dates son), and early postpartum period. When breastfeeding difficulties developed, the authors intervened with three consecutive (skin-to-skin) breastfeedings. During the first skin-to-skin breastfeeding, the mother stopped crying, shared self-disparaging emotions, and then began relaxing and "taking-in" her new baby. Breastfeeding continues at 1 year.

Acute stress impairs recognition for positive words--association with stress-induced cortisol secretion

Some studies suggest that stress-induced effects of cortisol on memory are modulated by the valence of the stimuli to be learned and retrieved. The present study investigated the effect of acute stress-induced cortisol secretion on acquisition and retrieval of pleasant, unpleasant and neutral words. Sixty healthy men were randomly assigned to one of the three experimental groups. Participants were either exposed to a standardized laboratory stressor (the Trier Social Stress Test) before learning a wordlist, or before retrieval, or were not stressed. Free recall and recognition were tested 24 h later. Free recall was not affected by stress exposure. For recognition, there was no main effect of the stressor, but a main effect of valence and a valence by group interaction emerged: recognition for positive words was significantly impaired when subjects were stressed before retrieval. In addition, a positive correlation between the cortisol response and errors of commission was found. The results suggest that acute stress impairs memory for positive stimuli and that stress-induced cortisol secretion interferes with accuracy of memory retrieval, i.e. the ability to discriminate true memories from false ones.

Breastfeeding and Maternal Stress Response and Health

This article reviews findings on the maternal stress and health effects of lactation. Several significant associations have emerged. Compared with not breastfeeding, breastfeeding is associated with increased parasympathetic nervous system modulation, greater vascular stress response, lower perceived stress levels, and fewer depressive symptoms. Breastfeeding exclusively is associated with an attenuated initial sympathetic cardiac nervous system response to some laboratory stressors. Bottle-feeding is associated with increased sympathetic and decreased parasympathetic cardiac control. The act of breastfeeding is associated with decreased neuroendocrine response to stressors and decreased negative mood. Finally, breastfeeding is associated with enhanced physical and mental health compared with non-breastfeeding.

Angiotensin II receptors in the arcuate nucleus mediate stress-induced reduction of prolactin secretion in steroid-primed ovariectomized and lactating rats

Angiotensin II (Ang II) is a peptide that exerts an inhibitory effect upon pituitary prolactin (PRL) release through the hypothalamic arcuate nucleus (ARC). Since both PRL and Ang II are known to be affected by stress, the experiments reported here were conducted to investigate the possible participation of Ang II in the stress-induced response of PRL in situations in which pre-stress PRL levels are high, as during the PRL surge induced by estradiol (E(2)) and progesterone (P) in ovariectomized rats (OVXE(2)P) and lactating females on day 7 post-partum. Adult female rats were stereotactically implanted with bilateral guide-cannulae in the ARC; 3 days later, they were microinjected with saline or losartan and, after a 15-min interval, they were submitted to stress by ether inhalation during 1 min. Five minutes after stress, trunk blood samples were collected. Plasma PRL was measured by radioimmunoassay (RIA). In OVXE(2)P and lactating rats, a significant reduction in PRL levels was detected after stress compared to non-stressed animals. The microinjection of losartan in the ARC before stress blocked the reduction of PRL in both OVXE(2)P and lactating females. In conclusion, the stress-induced reduction of plasma PRL in OVXE(2)P and lactating rats is mediated by Ang II through AT(1) receptors in the ARC.

Methadone maintenance and lactation: a review of the literature and current management guidelines

Methadone offers significant therapeutic benefits to the population of pregnant, opiate-dependent women and is currently the treatment of choice for this group. Yet the problem of women who elect to breastfeed while on methadone maintenance frequently vexes providers. Although breast milk offers advantages clearly beneficial to the general population of infants, there is debate about recommending breastfeeding to postpartum women receiving methadone maintenance. Although previous research has shown that amounts of methadone in breast milk appear to be very small, and therefore breastfeeding seems to be safe, women on methadone do not often breastfeed, for a variety of reasons. This article provides an overview of the issues facing providers in treating methadone-maintained women who elect to breastfeed. A comprehensive review of existing literature on the subject is offered, along with clinical advice for practitioners providing care to this population of women and children.

Maternal and fetal hypothalamic-pituitary-adrenal axes during pregnancy and postpartum

The principal modulators of the hypothalamic-pituitary-adrenal (HPA) axis are corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP). Corticotropin-releasing hormone is not exclusively produced in the hypothalamus. Its presence has been demonstrated at peripheral inflammatory sites. Ovulation and luteolysis bear characteristics of an aseptic inflammation. CRH was found in the theca and stromal cells as well as in cells of the corpora lutea of human and rat ovaries. The cytoplasm of the glandular epithelial cells of the endometrium has been shown to contain CRH and the myometrium contains specific CRH receptors. It has been suggested that CRH of fetal and maternal origin regulates FasL production, thus affecting the invasion (implantation) process through a local auto-paracrine regulatory loop involving the cytotrophoblast cells. Thus, the latter may regulate their own apoptosis. During pregnancy, the plasma level of circulating maternal immunoreactive CRH increases exponentially from the first trimester of gestation due to the CRH production in the placenta, decidua, and fetal membranes. The presence in plasma and amniotic fluid of a CRH-binding protein (CRHbp) that reduces the bioactivity of circulating CRH by binding is unique to humans. Maternal pituitary ACTH secretion and plasma ACTH levels rise during pregnancy-though remaining within normal limits-paralleling the rise of plasma cortisol levels. The maternal adrenal glands during pregnancy gradually become hypertrophic. Pregnancy is a transient, but physiologic, period of hypercortisolism. The diurnal variation of plasma cortisol levels is maintained in pregnancy, probably due to the secretion of AVP from the parvicellular paraventricular nuclei. CRH is detected in the fetal hypothalamus as early as the 12th week of gestation. CRH levels in fetal plasma are 50% less than in maternal plasma. The circulating fetal CRH is almost exclusively of placental origin. The placenta secretes CRH at a slower rate in the fetal compartment. AVP is detected in some neurons of the fetal hypothalamus together with CRH. AVP is usually detectable in the human fetal neurohypophysis at 11 to 12 weeks gestation and increases over 1000-fold over the next 12 to 16 weeks. The role of fetal AVP is unclear. Labor appears to be a stimulus for AVP release by the fetus. The processing of POMC differs in the anterior and intermediate lobes of the fetal pituitary gland. Corticotropin (ACTH) is detectable by radioimmunoassay in fetal plasma at 12 weeks gestation. Concentrations are higher before 34 weeks gestation, with a significant fall in late gestation. The human fetal adrenal is enormous relative to that of the adult organ. Adrenal steroid synthesis is increased in the fetus. The major steroid produced by the fetal adrenal zone is sulfoconjugated dehydroepiandrosterone (DHEAS). The majority of cortisol present in the fetal circulation appears to be of maternal origin, at least in the nonhuman primate. The fetal adrenal uses the large amounts of progesterone supplied by the placenta to make cortisol. Another source of cortisol for the fetus is the amniotic fluid where cortisol converted from cortisone by the choriodecidua, is found. In humans, maternal plasma CRH, ACTH, and cortisol levels increase during normal labor and drop at about four days postpartum; however, maternal ACTH and cortisol levels at this stage are not correlated. In sheep, placental CRH stimulates the fetal production of ACTH, which in turn leads to a surge of fetal cortisol secretion that precipitates parturition. The 10-day-long intravenous administration of antalarmin, a CRH receptor antagonist, significantly prolonged gestation compared to the control group of animals. Thus, CRH receptor antagonism in the fetus can also delay parturition. The HPA axis during the postpartum period gradually recovers from its activated state during pregnancy. The adrenals are mildly suppressed in a way analogous to postcure Cushing's syndrome. Provocation testing has shown that hypothalamic CRH secretion is transiently suppriently suppressed at three and six weeks postpartum, normalizing at 12 weeks.

Social support and oxytocin interact to suppress cortisol and subjective responses to psychosocial stress

BACKGROUND

The presence of social support has been associated with decreased stress responsiveness. Recent animal studies suggest that the neuropeptide oxytocin is implicated both in prosocial behavior and in the central nervous control of neuroendocrine responses to stress. This study was designed to determine the effects of social support and oxytocin on cortisol, mood, and anxiety responses to psychosocial stress in humans.

METHODS

In a placebo-controlled, double-blind study, 37 healthy men were exposed to the Trier Social Stress Test. All participants were randomly assigned to receive intranasal oxytocin (24 IU) or placebo 50 min before stress, and either social support from their best friend during the preparation period or no social support.

RESULTS

Salivary free cortisol levels were suppressed by social support in response to stress. Comparisons of pre- and poststress anxiety levels revealed an anxiolytic effect of oxytocin. More importantly, the combination of oxytocin and social support exhibited the lowest cortisol concentrations as well as increased calmness and decreased anxiety during stress.

CONCLUSIONS

Oxytocin seems to enhance the buffering effect of social support on stress responsiveness. These results concur with data from animal research suggesting an important role of oxytocin as an underlying biological mechanism for stress-protective effects of positive social interactions.

Brain mechanisms underlying emotional alterations in the peripartum period in rats

In the period before and after parturition, i.e., in pregnancy and lactation, a variety of neuroendocrine alterations occur that are accompanied by marked behavioral changes, including emotional responsiveness to external challenging situations. On the one hand, activation of neuroendocrine systems (oxytocin, prolactin) ensures reproduction-related physiological processes, but in a synergistic manner also ensures accompanying behaviors necessary for the survival of the offspring. On the other hand, there is a dramatic reduction in the responsiveness of neuroendocrine systems to stimuli not relevant for reproduction, such as the hypothalamo-pituitary-adrenal (HPA) axis responses to physical or emotional stimuli in both pregnant and lactating rats. With CRH being the main regulator of the HPA axis, downregulation of the brain CRH system may result in various behavioral, in particular emotional, adaptations of the maternal organisms, including changes in anxiety-related behavior. In support of this, the lactating rat becomes less emotionally responsive to novel situations, demonstrating reduced anxiety, and shows a higher degree of aggressive behavior in the test for agonistic behavior as well as in the maternal defense test. These changes in emotionality are independent of the innate (pre-lactation) level of anxiety and are seen in both rats bred for high as well as low levels of anxiety. Both brain oxytocin and prolactin, highly activated at this time, play a significant role in these behavioral and possibly also neuroendocrine adaptations in the peripartum period.

Increased hypothalamic expression of prolactin in lactation: involvement in behavioural and neuroendocrine stress responses

Prolactin (PRL) has recently been shown to exert an anxiolytic effect in male and virgin female rats, as well as an inhibitory tone on hypothalamic-pituitary-adrenal (HPA) axis activity. Reduced emotional and neuroendocrine stress responses have been described in lactation, a time of high blood PRL levels. Here we tested brain PRL-receptor (PRL-R)-mediated effects on anxiety, maternal behaviour, HPA axis and oxytocin stress responses in lactating rats. Chronic intracerebroventricular (i.c.v.) infusion of antisense oligonucleotides against the long form of the PRL-R (AS; osmotic minipump, 0.5 microg/0.5 microL/h) in order to downregulate brain PRL-R expression increased the anxiety-related behaviour on the elevated plus maze (P < 0.01) compared with mixed bases- and vehicle-treated rats. Also, PRL-R AS treatment impaired maternal behaviour (P < 0.05), whereas physiological parameters of lactation (weight gain of the litter, number of milk ejection reflexes during a 20-min suckling period) were not affected. PRL-R AS treatment further evoked an increase (P < 0.05) in the stress-induced adrenocorticotropin release, demonstrating an inhibitory role of PRL on HPA axis responses in lactation. Inhibition of stress responses of the oxytocin system by brain PRL was evidenced by higher stress-induced (P < 0.05) plasma oxytocin concentration in PRL-R AS-treated lactating rats and, in contrast, decreased stress-induced oxytocin release (P < 0.01) in chronic i.c.v. ovine PRL-treated (1 microg/0.5 microL/h) virgin rats. Finally, an increased expression of the hypothalamic PRL gene was seen by RT-PCR in pregnancy and lactation, suggesting an activated state of the brain PRL system during the peripartum period. In summary, activation of the brain PRL system in the peripartum period significantly contributes to emotional and neuroendocrine adaptations, including downregulation of the responsiveness of the HPA axis and oxytocin systems to stressors seen at this time.