Hormone levels in neonatal hair reflect prior maternal stress exposure during pregnancy

Echoes of conflict and displacement in maternal health: Life-course violence, timing, and maternal stress after childbirth at the northern Thailand-Myanmar border

Armed conflict, displacement, and related violence is escalating globally, concentrated among civilians and migrants in border areas, and poses grave harms to women and children. The current study investigates how women's life-course experiences of conflict and displacement are linked to maternal stress and health outcomes after childbirth at the Thailand-Myanmar border, specifically stress, mental health, and cardiometabolic outcomes. Analyses are based on a cross-sectional population-based maternal and child health survey of 701 mothers, collected in 2017-18 in northern Thailand along the Myanmar border, including in camps, worksites, and residential homes. Results suggest that how conflict violence shapes contemporary stress and health depends on the outcome, level and timing of conflict violence exposure, and subsequent contextual threats and deprivation in displacement contexts. Past conflict violence was associated with symptoms of perceived stress (PS) and generalized anxiety disorder (GAD) but not depression. It was also associated with hypothalamic-pituitary-adrenal (HPA) axis activity (hair cortisol concentration) and adiposity (waist circumference and waist-to-hip ratio). Additionally, past conflict violence that began in childhood was particularly salient for PS, GAD, and adiposity; and level and timing of violence were salient jointly for HPA activity. Post-displacement factors also independently predicted higher blood pressure and played a potentially partial mediating role in the association between conflict exposure and both PS and GAD symptoms.

Higher prenatal anxiety predicts lower neonatal hair cortisol

BACKGROUND

Prenatal glucocorticoids are one of the most widely proposed prenatal programming mechanisms, yet few studies exist that measure fetal cortisol via neonatal hair. Neonatal hair provides a window into the fetal experience and represents cortisol accumulation in the third trimester of pregnancy. In the current study, we test the links between two types of anxiety over the course of gestation (pregnancy-related anxiety and general anxiety) with neonatal hair cortisol.

METHOD

Pregnant individuals (N = 107) and their neonates (59.8% female) participated in the current study. Prenatal pregnancy-related anxiety and general anxiety were measured using the Pregnancy Related Anxiety Scale (PRAS) and the State-Trait Anxiety Inventory (STAI), in each trimester of pregnancy. Hierarchical linear modeling was used to model the intercept and slope of each type of anxiety over gestation. Neonatal hair samples were collected shortly after birth (Median days = 1.17, IQR = 0.75-2.00).

RESULTS

Both higher pregnancy-related anxiety and general anxiety at the beginning of pregnancy and a flatter decline of pregnancy-related anxiety over gestation were associated with lower neonatal hair cortisol. After inclusion of gestational age at birth and parity as covariates, pregnancy-related anxiety (intercept: β = -0.614, p =.012; slope: β = -0.681, p =.006), but not general anxiety (intercept: β = -0.389, p =.114; slope: β = -0.302, p =.217) remained a significant predictor. Further, when both general and pregnancy-related anxiety were entered into the same model, only pregnancy-related anxiety (intercept and slope) were significant predictors of neonatal hair cortisol, indicating an association with pregnancy-related anxiety above and beyond general anxiety.

CONCLUSION

Cortisol plays a central role in maturation of fetal organ systems, and at the end of gestation, higher cortisol has beneficial effects such as promoting fetal lung maturation. Further, lower maternal cortisol is linked to less optimal cognitive development and altered brain development. As maternal higher anxiety in early pregnancy and a flatter decrease over time are both associated with lower neonatal hair cortisol, maternal pregnancy-related anxiety could be a target of future intervention efforts.

Amniotic fluid cortisol predicts neonatal and infant development in non-stressed rhesus monkeys: Implications for prenatal stress

Prenatal stress adversely affects offspring development, with fetal cortisol (CORT) exposure being a primary hypothesized mechanism for stress-induced developmental deficits. Fetal CORT exposure can be assessed via measurements in amniotic fluid. However, in humans, amniocentesis is typically only performed for clinical reasons such as karyotyping; thus, amniotic fluid CORT cannot be obtained from a random sample. To test the hypothesis that fetal CORT exposure predicts neonatal and infant development in healthy primates, we measured amniotic fluid CORT in N = 18 healthy rhesus macaque (Macaca mulatta) dams (50:50 female:male infants) between 80 and 124 days gestation (mean ± SEM = 98.3 ± 2.9 days out of 165 days gestational length; i.e., second trimester). Maternal hair cortisol concentrations (HCCs) were assessed throughout pregnancy and lactation. Offspring were assessed for physical growth, neurological development, cognitive development, and HCCs across postnatal days 30-180. Controlling for gestational age at amniocentesis, higher amniotic fluid CORT significantly predicted slower infant growth rate (g/day) in the first 30 days (β = -0.19; R2 = 0.71, p = .008), poorer sensorimotor scores on the day 30 neonatal assessment (β = -0.28; R2 = 0.76, p = .015), and longer time to complete training (β = 0.48; R2 = 0.54, p = .026), but better performance (β = 0.91; R2 = 0.60, p = .011) on a discrimination cognitive task at 120-180 days. Amniotic fluid CORT was not associated with maternal or infant HCCs. Although these results are correlative, they raise the intriguing possibility that fetal CORT exposure in non-stress-exposed primates, as measured by amniotic fluid CORT, programs multiple aspects of neonatal and infant development. On the other hand, amniotic fluid CORT may not relate to chronic CORT levels in either mothers or infants when assessed by hair sampling.

Can we influence the neurological development and hair cortisol concentration of offspring by reducing the stress of the mother during pregnancy? A randomized controlled trial

The objective was to evaluate the effects of a stress management cognitive behavioural therapy followed during pregnancy on subsequent childhood on hair cortisol at birth and on neurodevelopment and Hair Cortisol Concentrations (HCC) at 6 months of age. The study sample included 48 pregnant women, divided into two groups: 24 women in the Therapy Group (TG) and 24 women who received standard pregnancy care (control group (CG); CG). To test the therapy efficacy, an evaluation of the HCC and psychological stress, psychopathological symptomatology and resilience was conducted before and after the treatment. The level of cortisol in their hair was obtained during pregnancy and that of their babies at birth. Six months after birth, a cortisol sample was taken from the hair and the babies' neurodevelopment was evaluated based on a Bayley-III test. The TG presented reductions in psychological stress and psychopathological symptomatology after treatment. On the other hand, the CG increased their cortisol concentrations between the pre and post intervention, remaining stable in the TG. Moreover, results showed that TG babies had lower cortisol concentrations at birth and obtained significantly higher cognitive and motor development scores at 6 months. These findings support that providing psychological care to pregnant women may not only have a benefit on these women's mental state, but may also benefit the neurodevelopment of their offspring.

Hair glucocorticoids are not a historical marker of stress - Exploring the time-scale of corticosterone incorporation into hairs in a rat model

Hair glucocorticoids are increasingly popular biomarkers, used across numerous research fields, and studied species, as a measure of stress. Although they are suggested to be a proxy of the average HPA axis activity spanning a period of weeks or months into the past, this theory has never been tested. In the present study, adrenalectomized rats with no endogenous (adrenal) glucocorticoid production were used to study how circulating glucocorticoid levels would be reflected in the glucocorticoid levels found in hair samples. By dosing the animals daily with high levels of corticosterone for seven days, while sampling hairs before, during, and after treatments, a timeline for glucocorticoid uptake into hairs was constructed. This kinetic profile was compared to two hypothetical models, and the theory that hair glucocorticoids are a record of historical stress had to be rejected. Corticosterone concentrations in hairs were found to increase within three hours of the first injection, the highest concentrations were found on the seventh day of treatments, and the decrease in concentrations post-treatment suggests rapid elimination. We speculate that hair glucocorticoid levels can only be used to characterize a stress-response for a few days following a postulated stressor. An updated model, where glucocorticoids diffuse into, along, and out of hairs needs to be adopted to reconcile the experimentally obtained data. The inescapable consequence of this updated model is that hair glucocorticoids become a marker of - and can only be used to study - recent, or ongoing, stress, as opposed to historical events, weeks or months in the past.

Prolonged Physiological Stress Is Associated With a Lower Rate of Exploratory Learning That Is Compounded by Depression

BACKGROUND

Stress is a major risk factor for depression, and both are associated with important changes in decision-making patterns. However, decades of research have only weakly connected physiological measurements of stress to the subjective experience of depression. Here, we examined the relationship between prolonged physiological stress, mood, and explore-exploit decision making in a population navigating a dynamic environment under stress: health care workers during the COVID-19 pandemic.

METHODS

We measured hair cortisol levels in health care workers who completed symptom surveys and performed an explore-exploit restless-bandit decision-making task; 32 participants were included in the final analysis. Hidden Markov and reinforcement learning models assessed task behavior.

RESULTS

Participants with higher hair cortisol exhibited less exploration (r = -0.36, p = .046). Higher cortisol levels predicted less learning during exploration (β = -0.42, false discovery rate [FDR]-corrected p [pFDR] = .022). Importantly, mood did not independently correlate with cortisol concentration, but rather explained additional variance (β = 0.46, pFDR = .022) and strengthened the relationship between higher cortisol and lower levels of exploratory learning (β = -0.47, pFDR = .022) in a joint model. These results were corroborated by a reinforcement learning model, which revealed less learning with higher hair cortisol and low mood (β = -0.67, pFDR = .002).

CONCLUSIONS

These results imply that prolonged physiological stress may limit learning from new information and lead to cognitive rigidity, potentially contributing to burnout. Decision-making measures link subjective mood states to measured physiological stress, suggesting that they should be incorporated into future biomarker studies of mood and stress conditions.

Hair cortisol and dehydroepiandrosterone sulfate concentrations in healthy beef calves from birth to 6 months of age

Cortisol (C) and dehydroepiandrosterone (DHEA) are recognized as the main fetal steroids, and they are likely to influence fetal development and have long-term effects on newborn hypothalamic-pituitary-adrenal axis (HPA) function. DHEA is often measured as its sulfates and expressed as DHEA-S. Hair analysis represents a promising methodological approach for the non-invasive measurement of steroids, allowing for a retrospective analysis of the total exposure to steroids over time, and avoiding the influence of acute events or circadian fluctuations. Hair cortisol and DHEA concentrations have been investigated in cows, but no studies have been performed on calves. The object of this study was to evaluate hair cortisol (HC) and hair DHEA-S (HDHEA-S) concentrations in beef calves from birth to six months of age. Hair samples of 12 beef calves (seven males, five females) were firstly collected at birth (T1) and then every three weeks up to six months of age (T2-T10), collecting only the re-grown hair. HC and HDHEA-S were analyzed by radioimmunoassay (RIA). Calves sex, weight and APGAR score were registered immediately after birth. Statistical analysis revealed that both HC and HDHEA-S were influenced by sampling time (P < 0.001). HC concentrations were higher at T1 compared to all subsequent samplings (T2-T10, P < 0.01); HC concentrations were higher at T2 compared to T4-T10 (P < 0.01), while no further changes were detected from T3 onward. Higher HDHEA-S concentrations were registered at T1, T2 and T3 compared to all the other samplings (P < 0.01). No correlation was found between hair concentrations of both steroids and calf sex or birthweight. APGAR score was negatively correlated only with HC at birth (P < 0.05). These data demonstrate that C and DHEA-S are quantifiable in the hair of calves and are influenced by their age. The higher HC detected at birth (T1) probably reflects the high serum C concentrations present late in pregnancy and increased by the fetal HPA axis, by which parturition is initiated in cows. The highest HDHEA-S at birth (T1) in calves indicates that the largest amounts of DHEA and its sulfates are produced during fetal development. Moreover, the findings of higher HC at three weeks after birth and of higher HDHEA-S until six weeks after birth, suggest that C and DHEA secretion continues also beyond birth, and that these steroids could be involved in the events occurring during the challenging first weeks of age in the calf.

Getting under the skin: Physiological stress and witnessing paternal arrest in young children with incarcerated fathers

U.S. jails see nearly 11 million annual admissions, rates that disproportionately affect men of color-more than half of whom are fathers. An estimated 7% of U.S. children experience the incarceration of a parent, increasing their risk for poor developmental and health outcomes. Although stress processes are often suggested as an underlying mechanism linking paternal incarceration to child well-being, few studies have examined such links. To study how witnessing a father's arrest prior to incarceration in jail relates to children's stress processes, we collected data on 123 individuals from 41 families with young children whose father was in jail, including collecting hair from 41 children, and analyzed their cumulative stress hormones, cortisol, and cortisone. Results indicate that children had higher cumulative stress hormone concentrations when they witnessed their father's arrest. Moreover, there was evidence of a blunted stress reaction in children who witnessed the arrest and who also had high levels of ongoing behavioral stress symptoms, similar to findings in Post-Traumatic Stress Disorder studies. Long-term exposure to stress can have deleterious effects on children's brain development, further increasing risk for developmental psychopathology. Findings have implications for criminal justice approaches that safeguard children during parental arrest.

Perinatal determinants of neonatal hair glucocorticoid concentrations

Adult hair glucocorticoid concentrations reflect months of hypothalamic-pituitary-adrenal axis activity. However, little is known about the determinants of neonatal hair glucocorticoids. We tested associations between perinatal exposures and neonatal hair glucocorticoids. Cortisol and cortisone were measured by LC-MS/MS in paired maternal and infant hair samples collected within 10 days of birth (n = 49 term, n = 47 preterm), with neonatal samples collected at 6-weeks in n = 54 preterm infants. We demonstrate cortisol accumulation in hair increases with fetal maturity, with hair cortisol being higher in term than preterm born infants after delivery (median 401 vs 106 pg/mg; p < 0.001). In term born infants, neonatal hair cortisol is positively associated with maternal hair cortisol concentration (β = 0.240, p = 0.045) and negatively associated with birthweight z-score (β = -0.340, p = 0.006). Additionally, being born without maternal labour is associated with lower hair cortisol concentrations (β = -0.489, p < 0.001) and a lower ratio of cortisol to cortisone (β = -0.484, p = 0.001). In preterm infants, histological chorioamnionitis is associated with a higher cortisol to cortisone ratio in hair (β = 0.459, p = 0.001). In samples collected 6 weeks after preterm birth, hair cortisol concentration is associated with cortisol hair concentrations measured after birth (β = 0.523, p < 0.001), chorioamnionitis (β = 0.250, p = 0.049) and postnatal exposures including intravenous hydrocortisone therapy (β = 0.343, p < 0.007) and neonatal sepsis (β = 0.290, p = 0.017). In summary, neonatal hair cortisol is associated with birth gestation, maternal hair cortisol concentration and fetal growth. Additionally, exposures at delivery are important determinants of hair cortisol, and should be considered in the design of future research investigating how neonatal hair cortisol relates to prenatal exposures or fetal development.

Within-person changes of cortisol, dehydroepiandrosterone, testosterone, estradiol, and progesterone in hair across pregnancy, with comparison to a non-pregnant reference group

The literature on hormone changes in pregnancy has focused largely on cortisol, and changes in sample average concentrations. Within-person changes and variability in hormone concentrations are less commonly reported, particularly for sex hormones, and especially measured in hair. Using a prospective sample of pregnant women and a non-pregnant comparison group, we examined changes in five steroid hormones in hair. Non-pregnant women were recruited from the same area with parallel procedures and assessment timeline. Participants include 68 women (34 pregnant, average age ​= ​29.14, and 34 non-pregnant; average age ​= ​27.18) who were predominately non-Hispanic White (83%), and above the 2020 poverty line (75%). Pregnant women provided 3 ​cm hair samples and completed questionnaires three times during pregnancy: 1) at 12 weeks, 2) at 26 weeks, and 3) at 38 weeks. Non-pregnant women provided 3 ​cm hair samples and completed questionnaires three times, at baseline, 14 weeks later, and 12 weeks after that to mirror the assessment schedule of the pregnant group. There was clear evidence that progesterone was higher initially and increased dramatically across pregnancy whereas non-pregnant patterns showed no systematic change. There was suggestive evidence that cortisol and estradiol increased over pregnancy and in non-pregnant women similarly across the same time course. There was suggestive evidence that DHEA decreased across pregnancy, particularly early in pregnancy, differently from patterns in non-pregnant women over the same time course. Most importantly, there was substantial variability of hormone concentrations and many different within-person patterns of changes in these hormones over time, with little evidence of systematic change or stability within-individuals. Moving beyond discussing sample averages to including within-person and non-linear changes in studies of hormones-behavior associations during pregnancy is an important future direction for further investigation.

•

We describe within-person hormone changes in pregnant and non-pregnant women.

•

There were many observed patterns of change over time within individuals.

•

Average hair progesterone increased and DHEA decreased across early pregnancy.

•

Average hair cortisol and estradiol weakly increased in both groups of women.

•

There was far more variability over time than systematic change or stability.

Endocrine Insights into the Pathophysiology of Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a class of neurodevelopmental disorders that affects males more frequently than females. Numerous genetic and environmental risk factors have been suggested to contribute to the development of ASD. However, no one factor can adequately explain either the frequency of the disorder or the male bias in its prevalence. Gonadal, thyroid, and glucocorticoid hormones all contribute to normal development of the brain, hence perturbations in either their patterns of secretion or their actions may constitute risk factors for ASD. Environmental factors may contribute to ASD etiology by influencing the development of neuroendocrine and neuroimmune systems during early life. Emerging evidence suggests that the placenta may be particularly important as a mediator of the actions of environmental and endocrine risk factors on the developing brain, with the male being particularly sensitive to these effects. Understanding how various risk factors integrate to influence neural development may facilitate a clearer understanding of the etiology of ASD.

Assessment of prenatal stress-related cortisol exposure: focus on cortisol accumulation in hair and nails

Prenatal stress adversely affects offspring development. Although cortisol is hypothesized to be a key mediator of stress-induced developmental deficits, determining the amount of fetal cortisol exposure produced by maternal stress has proved challenging. Current approaches, such as measuring cortisol concentrations in maternal plasma, saliva, or urine, amniotic fluid, fetal plasma, or cord blood, all have significant limitations for assessing cumulative fetal cortisol exposure over time. A recently emerging approach is to measure cortisol concentrations in maternal hair and/or newborn hair or nail samples. Maternal hair cortisol potentially shows long-term production across each trimester of pregnancy, whereas neonatal hair or nail cortisol is thought to reflect mainly third trimester hormone accumulation. This review first describes fetal adrenocortical development, placental cortisol metabolism, and the various sources of fetal cortisol exposure across pregnancy. We then summarize the results obtained from "classical" methods of assessing prenatal cortisol exposure prior to the advent of hair and nail cortisol measurement. Lastly, we discuss the initial development and validation of the hair cortisol methodology, its subsequent application to studies of chronic stress, and recent findings regarding maternal and neonatal hair or nail cortisol concentrations in relation to prenatal stress and other variables of interest.

Prenatal maternal stress and child hair cortisol four years later: Evidence from a low-income sample

BACKGROUND

Maternal stress during pregnancy can influence the trajectory of fetal development, shaping offspring physiology and health in enduring ways. Some research implicates fetal programming of the hypothalamic-pituitary-adrenocortical (HPA) axis as a mediator of these effects. The present study is the first to examine child hair cortisol concentration (HCC) and maternal stress during pregnancy in a diverse, low-income sample.

METHODS

The sample consisted of 77 healthy, low-income (M annual income: $13,321), mother-children pairs (M child age = 3.81 years, SD = 0.43). The children were 57 % girls, 43 % boys. Mothers were 65 % Latina/Hispanic, 28 % Non-Hispanic White, 7% Black/African American. Maternal prenatal stress was measured with the Perceived Stress Scale administered by interview in the second and third trimesters, and again approximately four years later when child hair samples for assaying HCC were collected.

RESULTS

On average maternal perceived stress increased significantly across pregnancy, then returned to lower levels 4 years after birth. Regression analysis revealed that child HCC was not significantly predicted by maternal perceived stress at either single prenatal time point. Exploratory analysis revealed evidence of a relation between increases in maternal prenatal stress from second to third trimester and child HCC four years later (r = .37, p =  .04).

CONCLUSIONS

These results suggest that measures of prenatal maternal stress at any one time point may not be predictive of offspring long-term HPA output in low-income child samples, but that increases in stress levels across pregnancy may provide important information undetected by individual time point measures.

Prenatal traumatic stress and offspring hair cortisol concentration: A nine year follow up to the Red River flood pregnancy study

INTRODUCTION

Findings concerning the relationship between maternal prenatal and child cortisol concentrations are inconsistent. This study examined whether the influence of an objective traumatic stressor during pregnancy, distance from a natural flood disaster, moderated the association between prenatal maternal diurnal cortisol and 9-year old offspring hair cortisol concentrations.

METHODS

Data were collected from 56 of the mothers who took part in a study of flood-related pregnancy outcomes in 2009 and their children. Data included distance of the maternal home from evacuation areas, four maternal saliva cortisol assessments (waking, 30 min after waking, afternoon, and before bed) provided within 3-months of the flood crest and child hair samples to assess cortisol secretion over the past month.

RESULTS

There was a significant interaction between proximity to flooding during pregnancy and maternal cortisol AUC predicting child hair cortisol, after controlling for maternal age, gestational age at cortisol sampling, sex of the child, current socioeconomic status and current maternal stress. At greater distance from flooding (lower stress conditions) there was a non-statistically significant positive association between maternal cortisol and child cortisol. In contrast, living closer to flooding (higher stress conditions) produced a significant negative association between maternal and child cortisol.

CONCLUSION

Experiencing a traumatic stressor during pregnancy may alter maternal-fetal programming of the hypothalamic-pituitary-adrenal axis. The direct threat of flooding led to offspring cortisol concentrations that resembled cortisol production seen in mothers with symptoms of PTSD and their offspring. This alteration is evident in nine-year-old offspring and may help explain inconsistencies in the previous literature.

Maternal and Neonatal Hair Cortisol Levels Are Associated with Infant Neurodevelopment at Six Months of Age

Background: Maternal stress during pregnancy can affect fetal development during certain sensitive periods. Objective: To longitudinally assess maternal hair cortisol levels during pregnancy, and the postpartum along with neonatal hair cortisol levels that could be associated with infant neurodevelopment at six months of age. Methods: A sample of 41 pregnant women longitudinally assessed during the first, second, and third trimester and the postpartum, along with their 41 full-term neonates participated in this study. Hair cortisol levels were assessed from participants. Infant neurodevelopment was assessed by means of the Bayley Scale of Infants Development, Third Edition at age six months. Results: Maternal hair cortisol levels in the first and second trimester accounted for 24% and 23%, respectively, of variance of infant gross motor development (p < 0.05). Maternal hair cortisol levels during the postpartum accounted for 31% of variance of infant cognitive development (p < 0.05), and 25% of variance of infant gross motor development (p < 0.05). Neonatal hair cortisol levels accounted for 28% of variance of infant gross motor development (p < 0.05). Conclusions: The preconception and prenatal time are sensitive periods related to infant neurodevelopment along with the cortisol levels surrounding the fetus while in the womb. Pregnant women could be assessed for hair cortisol levels while attending a prenatal appointment.

A systematic review of studies utilizing hair glucocorticoids as a measure of stress suggests the marker is more appropriate for quantifying short-term stressors

Quantitating glucocorticoids (GCs) in hairs is a popular method for assessing chronic stress in studies of humans and animals alike. The cause-and-effect relationship between stress and elevated GC levels in hairs, sampled weeks later, is however hard to prove. This systematic review evaluated the evidence supporting hair glucocorticoids (hGCs) as a biomarker of stress. Only a relatively small number of controlled studies employing hGC analyses have been published, and the quality of the evidence is compromised by unchecked sources of bias. Subjects exposed to stress mostly demonstrate elevated levels of hGCs, and these concentrations correlate significantly with GC concentrations in serum, saliva and feces. This supports hGCs as a biomarker of stress, but the dataset provided no evidence that hGCs are a marker of stress outside of the immediate past. Only in cases where the stressor persisted at the time of hair sampling could a clear link between stress and hGCs be established.

Maternal Stress During Pregnancy Is Associated with Decreased Cortisol and Cortisone Levels in Neonatal Hair

BACKGROUND

Hair glucocorticoids (GCs) offer a retrospective view on chronic GC exposure. We assessed whether maternal pre- and postnatal stress was associated with neonatal and maternal hair GCs postpartum (pp).

METHODS

On the first day pp 172 mother-infant pairs donated hair, of whom 67 had consulted a centre of expertise for psychiatric disorders during pregnancy. Maternal stress was scored on the Hospital Anxiety and Depression Scale during the first/second (n = 46), third trimester (n = 57), and pp (n = 172). Hair cortisol and cortisone levels were determined by liquid chromatography-tandem mass spectrometry, and associations with maternal hospital anxiety subscale (HAS) and hospital depression subscale (HDS) scores, and antidepressant use were analyzed with linear regression.

RESULTS

Neonatal hair GCs were negatively associated with elevated HAS-scores during the first/second trimester, log 10 (β [95% CI]) cortisol -0.19 (-0.39 to 0.02) p = 0.07, cortisone -0.10 (-0.25 to 0.05) p = 0.17; third trimester, cortisol -0.17 (-0.33 to 0.00) p = 0.05, cortisone -0.17 (-0.28 to -0.05) p = 0.01; and pp, cortisol -0.14 (-0.25 to -0.02) p = 0.02, cortisone -0.07 (-0.16 to 0.02) p = 0.10. A similar pattern was observed for elevated HDS-scores. Maternal hair GCs were positively associated with elevated HAS-scores pp (cortisol 0.17 [0.01 to 0.32] p = 0.04, cortisone 0.18 [0.06 to 0.31] p = 0.01), but not prenatally or with elevated HDS-scores. Antidepressant use was associated with elevated maternal hair GCs (p ≤ 0.05), but not with neonatal hair GCs.

CONCLUSION

Exposure to excessive pre- and perinatal maternal stress was associated with a decrease in neonatal hair GCs, while elevated stress-scores around birth were associated with increased maternal hair GCs and elevated stress-scores earlier in gestation were not associated with maternal hair GCs pp. Further studies are needed to test associations with infant neurodevelopment.

The use of hair cortisol for the assessment of stress in animals

The hair cortisol concentration (HCC) is assumed to be a retrospective marker of integrated cortisol secretion and stress over longer periods of time. Its quantification is increasingly used in psychoneuroendocrinological studies in humans, but also in animal stress and welfare research. The measurement of HCCs for the assessment of stress offers many considerable benefits for use in domesticated and wild animals, especially due to the easy and minimally invasive sampling procedure and the representation of longer time periods in one sample. This review aims to outline the different fields of application and to assess the applicability and validity of HCC as an indicator for chronic stress or long-term activity of the hypothalamic-pituitary-adrenal axis in wild and domesticated animals. Specific hair characteristics are presented and the advantages and limitations of using HCC are discussed. An overview of findings on the impact of stress- and health-related factors on HCCs and of diverse influencing factors causing variation in hair cortisol levels in different species is given. Recommendations for the use of hair cortisol analysis are proposed and potential fields of future research are pointed out. The studies indicate an effect of age and pregnancy on HCCs, and cortisol incorporation into hair was also found to depend on hair colour, body region, sex and season of year, but these results are less consistent. Furthermore, the results in animals show that a wide array of stressors and pathological conditions alters the cortisol concentrations in hair and that HCC thereby provides a reliable and valid reflection of long-term cortisol secretion in many species. However, more research is necessary to investigate the underlying mechanisms of cortisol incorporation into the hair and to explore the hair growth characteristics in the species of interest. To overcome confounding influences, the use of standardized sampling protocols is strongly advised.

Effects of parity and litter size on cortisol measures in commercially housed sows and their offspring

Breeding sows are regularly exposed to on-farm stressors throughout the duration of their production period. The impact of such stressors may differ for primi- and multiparous sows, as sows could learn to cope with stressors as they gain experience with them. If parity affects stress in sows, it may also impact their prenatal offspring through differential maternal stress. In addition to parity, litter size is another potential factor involved in stress of sows and piglets. Larger litters may be a source of discomfort for gestating sows, while it can result in intra-uterine growth restriction of piglets. In the current study, we aimed to assess whether parity and litter size affect cortisol measures in breeding sows and their offspring. To do this, we measured salivary cortisol concentrations of 16 primiparous and 16 multiparous sows at three time points: 1) while sows were group housed, 2) after sows were separated from the group prior to moving to the farrowing unit and 3) after handling procedures. In addition, hair cortisol concentration was determined for the sows during late gestation and for their low birth weight (n = 63) and normal birth weight (n = 43) offspring on day 3 after birth, to reflect in-utero cortisol exposure. It was expected that if sows adapt to on-farm stressors, the more experienced, multiparous sows would show decreased stress responses in comparison to primiparous sows. However, we found a comparable acute stress response of primi- and multiparous sows to separation from the group. Handling procedures did not influence sows' salivary cortisol concentrations. Sows' hair cortisol concentration was positively correlated with litter size. Future research is needed to assess whether this finding reflects increased stress in sows carrying larger litters. Parity or litter size did not have a direct effect on their offspring's hair cortisol concentration. Larger litters did have a higher occurrence of low birth weight piglets. For these piglets, females had higher neonatal hair cortisol concentrations than males. Overall, our results indicate that breeding sows do not adapt to all on-farm stressors. In addition, litter size may influence HPA axis activity in both sows and piglets.

Parental habituation to human disturbance over time reduces fear of humans in coyote offspring

A fundamental tenet of maternal effects assumes that maternal variance over time should have discordant consequences for offspring traits across litters. Yet, seldom are parents observed across multiple reproductive bouts, with few studies considering anthropogenic disturbances as an ecological driver of maternal effects. We observed captive coyote (Canis latrans) pairs over two successive litters to determine whether among‐litter differences in behavior (i.e., risk‐taking) and hormones (i.e., cortisol and testosterone) corresponded with parental plasticity in habituation. Thus, we explicitly test the hypothesis that accumulating experiences of anthropogenic disturbance reduces parental fear across reproductive bouts, which should have disparate phenotypic consequences for first‐ and second‐litter offspring. To quantify risk‐taking behavior, we used foraging assays from 5–15 weeks of age with a human observer present as a proxy for human disturbance. At 5, 10, and 15 weeks of age, we collected shaved hair to quantify pup hormone levels. We then used a quantitative genetic approach to estimate heritability, repeatability, and between‐trait correlations. We found that parents were riskier (i.e., foraged more frequently) with their second versus first litters, supporting our prediction that parents become increasingly habituated over time. Second‐litter pups were also less risk‐averse than their first‐litter siblings. Heritability for all traits did not differ from zero (0.001–0.018); however, we found moderate support for repeatability in all observed traits (r = 0.085–0.421). Lastly, we found evidence of positive phenotypic and cohort correlations among pup traits, implying that cohort identity (i.e., common environment) contributes to the development of phenotypic syndromes in coyote pups. Our results suggest that parental habituation may be an ecological cue for offspring to reduce their fear response, thus emphasizing the role of parental plasticity in shaping their pups’ behavioral and hormonal responses toward humans.

Radiolabel validation of cortisol in the hair of rhesus monkeys

Analysis of cortisol in hair has become a widespread tool for assessment of hypothalamic-pituitary-adrenal (HPA) axis activity because of its ease of collection and its ability to provide cumulative data over a period of months. In order to meaningfully interpret hair cortisol, however a direct validation by radio-metabolism is required to understand cortisol incorporation into hair. Tritiated [3H]-cortisol was IV administered to adult rhesus monkeys to determine 1) if [3H] is found in the hair after injection of [3H]-cortisol, 2) the growth rate of hair and 3) the form in which cortisol is found in hair. Samples of hair were collected from newly and previously shaved patches at 14-days and 28-days after [3H]-cortisol injection. Hair was processed by external wash, grinding, and hormone extractions. Samples were separated by high-performance liquid chromatography (HPLC) and fractions were collected and radioactivity assessed. We found [3H] incorporated into the hair by the 14-day hair collection and no new radioactivity was found by the 28-day collection. Individual hair growth rate was highly variable between monkeys, indicating that the between-subject hair growth patterns were not consistent. Importantly, for the first time, we showed that systemically administered [3H]-cortisol was found in the hair as [3H]-cortisol and [3H]-cortisone, as well as other glucocorticoid metabolites.

Newborn infants' hair cortisol levels reflect chronic maternal stress during pregnancy

Cortisol obtained from hair samples represents a retrospective biomarker of chronic stress experienced by the subject in previous months. Although hair cortisol levels have been used to study the relationship between maternal and neonatal stress levels in primates, this has not yet been performed in humans using a longitudinal design and focusing specifically on this association. Therefore, the objective of this study was to determine whether a relationship existed between maternal psychological stress and hair cortisol levels during pregnancy and postpartum, and neonatal hair cortisol levels. The sample consisted of 80 pregnant women and their 80 newborn infants. We conducted a longitudinal assessment of hair cortisol levels, psychological stress, anxiety, and depression in the three trimesters of pregnancy and postpartum. After childbirth, neonatal hair cortisol levels were also measured. We found that maternal hair cortisol levels in the first trimester negatively predicted neonatal hair cortisol levels. Perceived stress in the third trimester of pregnancy also predicted lower neonatal cortisol, whereas pregnancy-specific stress in the same trimester had a positive relation with neonatal cortisol. Cortisol is essential for embryonic and fetal development; consequently, if fetal synthesis of cortisol is affected by high maternal cortisol levels, such development could be impaired.

A longitudinal study of hair cortisol concentrations in Macaca nemestrina mothers and infants

Cortisol is a well-known glucocorticoid that can be used as a biomarker of hypothalamic-pituitary-adrenocortical activity. To explore basal cortisol physiology during pregnancy and infancy in Macaca nemestrina monkeys, hair was collected from a convenience sample of 22 healthy mother-infant dyads. Adult females were housed in pairs as part of a small breeding colony at the Washington National Primate Research Center and infants were reared in a specialized nursery. Maternal samples were collected from females during a pregnancy-detection ultrasound and immediately following labor and delivery. Infant samples were collected at birth, 20 days, 4, 6, 8, and 10 months of age. Hair cortisol concentrations (HCCs) were determined using an enzyme immunoassay in washed and ground hair samples. Like human mothers, macaque HCCs rose during pregnancy (paired t = 5.8, df = 16, P < 0.001). Maternal HCCs at pregnancy-detection (114.2 ± 12.07 picogram/milligram [pg/mg]) were highly predictive of maternal HCCs at delivery (144.8 ± 13.60 pg/mg), suggesting a trait-like quality (r = 0.90, P < 0.001). When maternal HCCs were viewed on a continuum, the absolute rise in cortisol over the course of pregnancy was significantly related to newborn HCCs (r = 0.55, P = 0.02). Infant birth HCCs (1,027.43 ± 97.95 pg/mg) were seven times higher than maternal HCCs at delivery (paired t = 19.1, df = 16, P < 0.001). Higher birth HCCs were strongly associated with larger decreases in infant hair cortisol until 6 months of postnatal age when infant HCCs converged on values indistinguishable from adults. Overall, study results demonstrate a marked degree of fetal cortisol exposure during the latter part of gestation and suggest that the rise in maternal cortisol over pregnancy may play an influential role on HCCs in the newborn.

The quantification of reproductive hormones in the hair of captive adult brown bears and their application as indicators of sex and reproductive state

Recognizing the potential value of steroid hormone measurements to augment non-invasive genetic sampling, we developed procedures based on enzyme-linked immunoassays to quantify reproductive steroid hormone concentrations in brown bear (Ursus arctos) hair. Then, using 94 hair samples collected from eight captive adult bears over a 2-year period, we evaluated (i) associations between hair concentrations of testosterone, progesterone, estradiol and cortisol; (ii) the effect of collecting by shaving vs. plucking; and (iii) the utility of reproductive hormone profiles to differentiate sex and reproductive state. Sample requirements (125 mg of guard hair) to assay all hormones exceeded amounts typically obtained by non-invasive sampling. Thus, broad application of this approach will require modification of non-invasive techniques to collect larger samples, use of mixed (guard and undercoat) hair samples and/or application of more sensitive laboratory procedures. Concentrations of hormones were highly correlated suggesting their sequestration in hair reflects underlying physiological processes. Marked changes in hair hormone levels during the quiescent phase of the hair cycle, coupled with the finding that progesterone concentrations, and their association with testosterone levels, differed markedly between plucked and shaved hair samples, suggests steroids sequestered in hair were likely derived from various sources, including skin. Changes in hair hormone concentrations over time, and in conjunction with key reproductive events, were similar to what has been reported concerning hormonal changes in the blood serum of brown bears. Thus, potential for the measurement of hair reproductive hormone levels to augment non-invasive genetic sampling appears compelling. Nonetheless, we are conducting additional validation studies on hair collected from free-ranging bears, representative of all sex, age and reproductive classes, to fully evaluate the utility of this approach for brown bear conservation and research.

Gestational Timing of Prenatal Disturbance and Fetal Sex Determine the Developmental Outcomes

BACKGROUND

Maternal stress during pregnancy can have deleterious consequences, increasing risk for prematurity and low birth weight, as well as postnatal effects on emotional regulation and neuromotor development. It is less clear, however, whether moderate and brief gestational disturbances have similar effects.

OBJECTIVE

To determine the impact of a delimited period of moderate maternal stress on infant growth, emotional reactivity, and neurobehavioral maturity in a nonhuman primate model.

METHODS

Eighty-three infant rhesus monkeys were generated from disturbed pregnancies, either early or late gestation, and compared with 51 undisturbed infants. Maternal stress was induced with an acoustical startle protocol for 25% of gestation. Infant weights, anthropometrics, and neurobehavioral data were obtained. Analyses focused on differential effects of prenatal stress on male and female infants.

RESULTS

The disturbance manipulation elevated cortisol levels acutely in the gravid females and they gained less weight by term. Nevertheless, female infants from the early stress condition were significantly larger at birth. This differential growth trajectory was then sustained through 6 months of age. Infants from stress conditions were more emotionally reactive and evinced immature neuromotor reflexes, especially when gestated by late stress mothers.

CONCLUSIONS

Even moderate maternal disturbance impacted infant temperament and neuromotor development in this nonhuman primate model. Effects on fetal and infant growth differed from typical reports of growth inhibition, both in other animal species and human studies. The findings convey the importance of considering the duration and severity of prenatal insults, and the potential for fetal plasticity and recovery, permitting compensatory growth responses.