Experiences of discrimination during pregnancy predict altered neonatal hair cortisol at birth

Abstract

Objective:

Prenatal glucocorticoids (e.g., cortisol) are a widely proposed prenatal programming mechanism, yet few studies directly measure fetal cortisol. Neonatal hair provides a non-invasive method to assess fetal cortisol. The current studies test the association between maternal exposure to discrimination and fetal cortisol, as measured in neonatal hair, in two cohorts.

Methods Study 1:

Pregnant individuals (N=65) and their neonates (61.8% female) participated in study 1 between 2017–2021. Participants self-identified as Asian (6.2%), Black (21.5%), Latinx (35.4%), Multiracial or Multiethnic (35.4%), and Native Hawaiian or Pacific Islander (1.5%). Experiences of discrimination were measured using the Everyday Discrimination Scale. Neonatal hair samples were collected close to birth (Median_days=1.30, IQR_days=0.96–2.03).

Results Study 1:

Higher experiences of everyday discrimination among pregnant individuals were associated with lower hair cortisol levels in neonates (r=−.28, p=.031).

Methods Study 2:

Pregnant individuals of Mexican descent (N=73) and their neonates (50.7% female) participated in study 2 between 2017–2020. Participants reported on their exposure to experiences of discrimination using the Discrimination Stress Scale, and neonatal hair samples were collected shortly after birth (Median_days=13.0, IQR_days=11–18).

Results Study 2:

Those who had higher discrimination stress during pregnancy had neonates with higher cortisol than those with low discrimination (F(1,70)= 3.78, p=.03), but this relation did not remain significant after controlling for gestational age.

Conclusion:

Across two cohorts, higher experiences of discrimination were associated with alterations in neonatal hair cortisol. Both higher and lower neonatal hair cortisol are linked to poorer neonatal development, indicating that experiences of discrimination might be a potential source of health disparities in the next generation.

1. Introduction

Racial and ethnic heath disparities are well-documented (Mehta et al., 2013; Mukherjee et al., 2016). However, the biological pathways through which these disparities manifest and exert intergenerational consequences are understudied (Conradt et al., 2020; Green and Darity, 2010). Therefore, it is important to examine the ontogeny of health disparities and the role of the prenatal environment in the intergenerational transmission of health disparities. The Developmental Origins of Health and Disease (DOHaD) hypothesis posits that environmental exposures early in life, particularly in the prenatal period, can result in developmental alterations that have long-lasting health consequences for offspring health (Barker, 1998; Barker et al., 2002). Prenatal insults predict poor birth outcomes, stress physiology dysregulation, and altered brain development, all of which have long-term consequences for development (Barker, 1998; Davis and Sandman, 2010; Deer et al., 2023; Glynn et al., 2008; Irwin et al., 2021).

Alarming disparities exist within rates of preterm birth and other adverse birth outcomes (Moaddab et al., 2018; Petersen, 2019). Among pregnant individuals from marginalized backgrounds, experiences of discrimination (mistreatment or bias behavior towards a person based on identity or other characteristics) are a robust predictor of adverse birth outcomes (Conradt et al., 2020; Giurgescu et al., 2012; Scholaske et al., 2019). Reports of discrimination experiences by pregnant individuals predict preterm birth (Collins et al., 2000; Rosenberg et al., 2002a; van Daalen et al., 2022) as well as low birthweight (Earnshaw et al., 2013; Liu et al., 2023a). Further, emerging work indicates that prenatal experiences of discrimination have implications for infant outcomes, including greater negative emotionality and poorer self-regulation (Liu et al., 2023b; Rivera et al., 2024; Rosenthal et al., 2018). Despite evidence that maternal experiences of discrimination associates with birth outcomes (Larrabee Sonderlund et al., 2021), few studies have directly considered biological processes that may explain the relation between experiences of discrimination and child outcomes.

One biological process that is often proposed to underlie the association between maternal experiences of discrimination and offspring development is alterations in the hypothalamic-pituitary-adrenal (HPA) axis. The end product of the HPA axis, cortisol, is associated with long-term health outcomes, such as more negative affect in childhood and mental health disorders in adolescence (Davis et al., 2007; Essex et al., 2011; Van den Bergh et al., 2008). Classically, it has been difficult to measure the fetal HPA axis, with previous studies using invasive procedures such as amniotic fluid via amniocentesis or plasma via fetal blood draws for clinical testing (Gitau et al., 1998). Measurement of cortisol in hair has emerged as a useful method to measure long-term HPA activity in the perinatal period (D’Anna-Hernandez et al., 2011; Hoffman et al., 2017). Neonatal hair grows in utero as early as 22–26 gestational weeks (Gareri and Koren, 2010) and reflects fetal cortisol accumulation in the third trimester from three sources: 1) circulating maternal cortisol passed through the placenta, 2) fetal production, and 3) and fetal urinary excretion, which comprises amniotic fluid (Meyer & Novak, 2021). Thus, measuring newborn hair provides a non-invasive method to address in utero exposure to cortisol.

Experiences of discrimination are stressors that impact cortisol regulation. For example, experiences of discrimination are associated with higher hair cortisol concentrations in non-pregnant adults (Lehrer et al., 2020; Yip et al., 2021). Although it is known that prenatal experiences influence offspring cortisol regulation (Irwin et al., 2021; Molenaar et al., 2019; O’Connor et al., 2013), and that racial discrimination is related to alterations in cortisol responses in pregnant individuals (Chaney et al., 2019; Suglia et al., 2010), few studies have examined intergenerational consequences of discrimination for offspring cortisol. Pregnant individuals experiencing more ethnic discrimination during pregnancy had infants with larger cortisol reactivity response to a painful stressor (inoculation) at six weeks of age (Thayer and Kuzawa, 2015). Similarly, among Black infants, those whose mothers reported high levels of lifetime discrimination had higher cortisol reactivity to a physical assessment via the Neonatal Intensive Care Unit (NICU) Network Neurobehavioral Scale at two weeks of age (Hendrix et al., 2022). A third study also found that among Black infants, higher maternal experiences of discrimination were associated with higher cortisol reactivity to the Strange Situation procedure at one year of age (Dismukes et al., 2018). As overviewed in our conceptual diagram (see Figure 1), these studies document that discriminatory experiences are linked to altered cortisol regulation, and that there is evidence of intergenerational transmission. However, to our knowledge, the association between experiences of discrimination during pregnancy and neonatal hair cortisol has not been tested. Thus, this study will test the first part of the conceptual model, with the goal of future work to address the whole model.

Figure 1. Proposed Conceptual Model of the Biological Embedding of Prenatal Maternal Discrimination.

This study aims to address the hypothesis that maternal exposure to discriminatory experiences during pregnancy are associated with alterations to fetal cortisol exposure, as measured in neonatal hair. We test this hypothesis by using two cohorts from minoritized and marginalized backgrounds in two different immigrant destinations: an interior United States (US) city and a US border town. Differences in experiences of discrimination are observed based on structural differences by location, such as education, housing, discriminatory policies and migration history of communities (Flippen and Farrell-Bryan, 2021; Flippen and Parrado, 2015). Similarly, in work addressing the effects of maternal discrimination and maternal mental health in Latinas during a time of sociopolitical turmoil, discrimination varied by location (i.e. slight decrease in recent immigration destination vs. increase in border city), but a reduction in protective factors and an overall deterioration of mental health in both locations (Non et al., 2022). In addition, the maternal biological response stress to stress also varies by immigration stress in Latina mothers (Armah et al., 2024). In mothers who reported more immigration stress and higher endorsement of the traditional value of familism, psychophysiological stress regulation was increased as indexed by respiratory sinus arrhythmia (RSA). As policies and histories of immigration and discriminatory practices vary across the U.S. is important to investigate the relation between maternal experiences of discrimination and changes in stress biology in the mother/child dyad across multiple contexts. Thus, it was hypothesized fetal exposure to maternal discrimination in infants would be associated with differences in infant cortisol, that may vary by location.

2. Methods & Results

2.1. Methods Study 1: Interior City

2.1.1. Participants

Participants included 65 pregnant individuals and their neonates (60.0% female) from the Care Project, a longitudinal study beginning in pregnancy (Davis et al., 2018; Hankin et al., 2023). Recruitment occurred in obstetric and gynecological clinics in Denver, Colorado. All participants had a singleton intrauterine pregnancy, were proficient in English, were over the age of 18 and less than 25 gestational weeks at the time of recruitment. Participants were recruited into one of 3 groups: euthymic (absence of psychiatric condition), elevated depression symptoms randomized to enhanced usual care (EUC), and elevated depression symptoms randomized to interpersonal psychotherapy IPT). The latter two groups comprised participants with elevated depression symptoms who were recruited as part of a randomized clinical trial comparing the effect of IPT versus EUC to reduce depression during pregnancy (see Hankin et al., 2023 for additional details). Although not the focus of this report, briefly, IPT is an evidence-based therapy for depression that focuses on improving interpersonal relationships and social functioning, whereas EUC consisted of receiving standard of care through participants’ health providers with enhancement via an addition psychoeducation session with a clinician and ongoing depression symptom monitoring throughout pregnancy. Participants with major health conditions or substance use were excluded. Participants from racially and ethnically marginalized backgrounds in the sample were included in the current analyses. Exclusion criteria for the current analyses were: 1) neonatal hair sample collection more than three weeks after birth (n = 5), 2) inability to assay the hair sample (e.g., insufficient quantity of hair for assay; n = 10), and 3) exposure to prenatal steroids for fetal lung maturation (n = 7), resulting in an analytical sample of 65. Data was collected between 2017 and 2021.

2.1.2. Demographics

Participants self-identified as Asian (6.2%), Black (21.5%), Latinx (35.4%), Multiracial or Multiethnic (35.4%), and Native Hawaiian or Pacific Islander (1.5%). Most pregnant participants were born in the United States (74%) and all participants were English speaking. At time of recruitment, pregnant individuals were on average 28.7 years of age (SD = 5.1). Median household income was $40,000, and 35.3% of participants had at least a college degree. Participants identified the race/ethnicity of their neonate as Asian (4.6%), Black (23.1%), Latinx (30.8%), and Multiracial or Multiethnic (41.5%). Additional demographic information can be seen in Table 1.

Table 1.

Sample Characteristics for Study 1 and 2.

	Study 1 (n = 65)	Study 2 (n = 73)
Maternal characteristics	M ± SD; Range, %
Age (years)	28.7 ± 5.1; 20–42	29.7 ± 6.1; 18–44
Race/ethnicity
Asian	6.2%
Black/African American	21.5%
Latinx	35.4%	100%
Multiracial/multiethnic	35.4%
Native Hawaiian	1.5%
Born in the USA	74%	23.3%
Household income*	40,000; 23,000–72,000	24,000; 14,760–33,600
Education (highest degree)
Less than high school degree	9.2%	33.3%
High school, GED, or technical	32.3%	52.2%
College without a degree	23.1%	7.3%
Associate or Bachelor’s	26.1%	5.8%
Graduate or certificate	9.2%	1.4%
Cohabitating with a partner	69.2%	72.6%
Parity (first born)	30.8%	37%
Clinically relevant depression ŧ levels (early pregnancy)	29.4 %	32.2%
Infant characteristics	M ± SD; Range, or %
Age at hair collection (days)*	1.3; 0.9–2	13; 11–18
Sex (female)	60%	50.7%
Race/ethnicity
Asian	4.6%
Black/African American	23.1%
Latinx	30.8%	100%
Multiracial/multiethnic	41.5%
Gestational age (weeks)	39.1 ± 1.2; 36.4–41.6	39.1 ± 2.0; 28.6–43.7
Birth weight (grams)	3,234 ± 437.2; 2,230–4,080	3,281.6 ± 552.8; 1,048.9–4,621
Outcome variables	M ± SD; Range
Neonatal hair cortisol (pg/mg)	118.8 ± 98.4; 18.8–534.8	114.5 ± 61.5; 12.6–357.9
Neonatal hair cortisol (log10)	1.9 ± 0.4; 1.3–2.7	4.6 ± 0.6; 2.5–5.9

Note.

^*For household income and infant age at hair collection, medians and interquartile ranges were reported.

^ŧClinically relevant depressive symptoms were determined via the EPDS >13 for Study 1 and CESD>16 for Study 2

2.1.3. Procedure

During the second trimester of pregnancy (M_weeks = 28.78, SD_weeks = 4.32), participants reported on daily experiences of discrimination during their pregnancy. Shortly after birth, neonatal hair was collected by a trained research assistant or nurse (Median_days = 1.30, IQR_days = 0.96–2.03). The study was approved by the University of Denver and Colorado Multiple Institutional Review Board and participants were compensated at each research visit. All participants provided written and informed consent.

2.1.4. Measures

2.1.4.a. Discrimination.

The Everyday Discrimination Scale (Williams et al., 1997) was used to measure the occurrence of discrimination in participants’ day-to-day life. The scale asks participants to report how often in their day-to-day life one of 10 different experiences happened to them (e.g., treated with less respect than other people). Additionally, participants reported the main reason why they thought they experienced discrimination (i.e., because of race, ethnicity, gender). The responses were dichotomously coded (0 = did not experience, 1 = experienced) and the score was calculated by summing each response, making a possible range of 0, signifying no experiences of discrimination, to 10, signifying discrimination experienced in all situations. The Everyday Discrimination scale has been administered among racially/ethnically minoritized and marginalized pregnant people with good internal reliability of .84–.85 (Earnshaw et al., 2013). In the current study, the Cronbach’s alpha was .91.

2.1.4.b. Neonatal Hair Cortisol.

At birth, hair cortisol samples were collected from neonates close to the scalp from the nape of the neck. In utero hair follicle formation begins early in the second trimester and hair from the occipital area of the scalp, where collection occurred, does not enter the telogen phase or fall out until 8–12 weeks postnatal, thus is representative of in utero hair growth (Barth, 1987; Duggins and Trotter, 1950; Furdon and Clark, 2003). Hair cortisol collection and processing were conducted following protocols from Meyer and colleagues (2014). Infant hair length ranged from 0.50–3.10 cm (M_cm = 1.87, SD_cm = 0.51) and samples weighed at least 0.6 milligrams. Samples were stored in aluminum foil and envelopes to avoid contact with light until processing. Hair samples were assayed at the Center for Neuroendocrine Studies at the University of Massachusetts, Amherst. Hair samples were washed three times in isopropanol and dried for two to three days. Hair was then weighed, ground, and 1.5 milliliters of high-performance liquid chromatography-grade methanol was added to the microcentrifuge tubes and the samples were incubated at room temperature for 18–24 hours. After incubation, the tubes were centrifuged at 10,000 revolutions per minute (rpm) for five minutes at room temperature. Cortisol was extracted with a high-sensitivity enzyme immunoassay (EIA) assay buffer then assayed in duplicate using the Arbor Assays DetectX Cortisol enzyme immunoassay kit (intra-assay CV = 5.1%, inter-assay CV = 15.3%; Meyer et al., 2014). Neonatal hair cortisol data were log transformed for analysis following standards in the field (Miller and Plessow, 2013).

2.1.4.c. Birth Outcomes.

To collect information on gestational age at birth, parity, and neonatal sex, medical records were collected. Gestational age at birth was determined via the American College of Obstetricians and Gynecologists (ACOG) guidelines (ACOG, 2017).

2.1.5. Data Analysis Plan

Analyses were conducted using IBM SPSS Statistics (Version 28.0.1.1). Based on prior literature, gestational age at birth, neonatal sex, and parity (Hoffman et al., 2017; Hollanders et al., 2017; Koskivuori et al., 2023; van der Voorn et al., 2018; Wynne-Edwards et al., 2019), as well as group status in the intervention were assessed as covariates. Consistent with prior research (Deer et al., 2024) gestational age at birth (r = .30, p = .016) was positively correlated with neonatal hair cortisol. Neonatal sex (p = .874) and parity (p = .124) were not associated with neonatal hair cortisol. Neonatal hair cortisol differed by treatment group status (euthymic, IPT, or EUC); F(2,62) = 3.50, p = .036. Thus, treatment group status was covaried for in all of models with the euthymic group used as the reference group. A regression model was conducted to test whether the association between experiences of discrimination and neonatal hair cortisol persisted with covariates (Table 3).

Table 3.

Regression Analyses for Study 1 (Interior City) to Test the Association Between Fetal Exposure to Maternal Discrimination and Logged Neonatal Hair Cortisol Levels (n = 65).

Model	Predictors	B	SE	β	t	p
1	Everyday experiences of discrimination	−0.03	0.01	−.27	−2.21	.031*
2	Everyday experiences of discrimination	−0.02	0.01	−.25	−2.04	.046*
	IPT status	−0.12	0.09	−.16	−1.33	.187
	Gestational age at birth	0.08	0.04	.27	2.23	0.29*
3	Everyday experiences of discrimination	−0.03	0.01	−.29	−2.43	.018*
	IPT status	−0.13	0.09	−.17	−1.40	.165
	Parity	−0.06	0.03	−.21	−1.74	.088
4	Everyday experiences of discrimination	−0.03	0.01	−.30	−2.37	.021*
	IPT status	−0.11	0.10	−.14	−1.14	.257
	Neonatal sex	0.01	0.09	.01	0.09	.931

Notes.

^{^}p < .10

^*p < .05

^**p < .01

^***p < .001.

2.1.5. Results Study 1: Interior City

Participants reported experiencing discrimination in 5.8 out of 10 possible situations (SD = 3.6). Greater experiences of discrimination among pregnant individuals were associated with lower hair cortisol levels in neonates (r = −.27, p = .03; see Table 2). The association between experiences of everyday discrimination and neonatal hair cortisol (β = −.25, p = .046) persisted when covarying for intervention group status and gestational age at birth as well as parity and neonatal sex (Table 3). As some participants reported experiencing no discrimination (n = 10, 15.38%), sensitivity analyses were conducted to test whether there were differences in hair cortisol for neonates of pregnant individuals who reported any discrimination in comparison to those who reported no discrimination. Similar to continuous analysis, hair cortisol for neonates whose gestational parent reported any discrimination was lower than for neonates whose gestational parent reported no discrimination (t(63) = 2.18, p = .03; log10 hair cortisol means ± SD, no discrimination = 2.16±0.37, discrimination = 1.90±0.34).

Table 2.

Correlations Among Study Variables and Demographic Factors.

	Study 1
Study variables	1	2	3	4	5
1. Neonatal hair cortisol (log10)
2. Discrimination	−.27*
3. Household income	.02	.10
4. Gestational age at birth	.30*	−.19	.11
5. Parity	−.19	.03	−.12	−.24^
6. Neonatal sex	−.02	.07	−.23^	−.01	−.03
	Study 2
Study variables	1	2	3	4	5	6
1. Neonatal hair cortisol (log10)
2. Discrimination (early)	.01
3. Discrimination (late)	−.01	.67***
4. Household income	.17	.20	.09
5. Gestational age at birth	.65***	−.03	−.13	.06
6. Parity	−.21	−.09	−.16	.15	.20
7. Neonatal sex	.02	−.22^	−.11	.17	−.05	0.01

Notes.

^{^}p < .10

^*p < .05

^**p < .01

^***p < .001.

Newborn sex was coded as 0 = male, 1 = female. Discrimination was used as a continuous variable.

2.2. Methods Study 2: Border Town

2.2.1. Participants

Participants included 73 pregnant individuals of Mexican descent and their neonates (50.7% female). Recruitment occurred in community clinics in a border town in North County San Diego. All participants had a singleton intrauterine pregnancy, were proficient in English or Spanish, were between 18–45 years of age, and between gestational age 10–15 weeks at the time of recruitment. Participants with major health conditions or current substance use or psychiatric medication use were excluded. Exclusion criteria for the current analyses were: 1) neonatal hair sample collection more than 3 weeks after birth (n = 4), and 2) exposure to prenatal steroids for fetal lung maturation (n = 2). Data was collected between 2017 and 2020.

2.2.2. Demographics

All participants self-identified as Mexican, Mexican American or Chicana. Most participants were born in Mexico (66%), spoke Spanish as their primary language (70%) and had been in the US for an average of 16.13 years. At recruitment, pregnant individuals were on average 29.7 years of age (SD = 6.1). The median household income was $27,500 and 22% of participants had a college degree. Additional demographic information in Table 1.

2.2.3. Procedure

During the first (M_weeks = 12.96, SD_weeks = 2.26) and third trimesters of pregnancy, (M_weeks = 33.9, SD_weeks = 1.03), participants reported on experiences of discrimination. Within 2–3 weeks of birth, neonatal hair was collected by a trained research assistant (Median_days = 13.00, IQR_days =11 – 18). The study was approved by the California State University San Marcos Institutional Review Board and participants were compensated at each research visit. All participants provided written and informed consent.

2.2.4. Measures

2.2.4.a. Discrimination.

The Discrimination Stress Scale (DSS) assessed perceived racial/ethnic discrimination in everyday life due to ethnic minority status. The DSS is a 14-item scale that asks participants to choose from a range of discrimination-related experiences (e.g., being treated rudely or unfairly because of their race or ethnicity or have more barriers to overcome tan others because of your race) on a 4-point Likert Scale from 1 (never) to 4 (very often) (Flores et al., 2010, 2008) with good reliability in the current study (α=0.93). Given variability of reported rates of any discrimination in the study (1^st trimester: 31%; 3^rd trimester: 37%), perceived discrimination was dichotomized: 1) never experiencing discrimination or 2) at least sometimes. This dichotomization of the discrimination variable has been previously performed in Latinx populations with similar lifetime discrimination rates (Otiniano Verissimo et al., 2014).

2.2.4.b. Neonatal hair cortisol.

Within 2–3 weeks of birth, hair cortisol samples were collected from neonates close to the nape of the neck and wrapped in aluminum foil for storage as previously described (D’Anna-Hernandez et al., 2011). Infant hair length ranged from 0.70–3.60 cm (M_cm = 1.89 cm, SD_cm = 0.65). Hair samples were assayed at California State University, San Marcos. Neonatal hair was washed twice in isopropanol and dried for 4 days. Hair was then weighed and freeze-dried in liquid nitrogen before being ground to a powder using a Retsch ball mill for 10 min at 25 Hz. Cortisol was extracted from hair as previously described (D’Anna-Hernandez et al., 2011) and reconstituted with assay buffer and cortisol levels determined using a commercial high sensitivity EIA kit (Salimetrics, LLC) according to manufacturer’s directions. Intra-assay coefficient of variation (CV) is less than 9% and inter assay CV is less than 5%. Neonatal hair cortisol levels were log transformed for analysis (Miller and Plessow 2013).

2.2.4.c. Birth Outcomes.

Women self-reported on birth outcomes, which were then verified by medical records. Gestational age at birth was determined via ACOG guidelines (ACOG, 2017). Parity and neonatal sex were also extracted.

2.2.5. Data Analysis Plan

Analyses were conducted using IBM SPSS Statistics (Version 28.0.1.1). Based on prior literature, gestational age at birth, neonatal sex, and parity (Hoffman et al., 2017; Hollanders et al., 2017; van der Voorn et al., 2018) were assessed as covariates. Consistent with prior literature, later gestational age at birth was significantly correlated with higher neonatal hair cortisol (r = .65, p < 0.001). Neonatal sex (p > 0.05) and parity (p = −.21) were not associated with hair cortisol. To test the hypotheses that maternal discrimination is related to neonatal hair cortisol levels, univariate analyses with maternal discrimination (yes/no) as the fixed factor and log transformed hair cortisol as the dependent variable were conducted. Additional univariate analyses were performed with all covariates.

Results Study 2: Border Town

Experiences of perceived discrimination among pregnant individuals in the first trimester were not significantly associated with high fetal hair cortisol levels in neonates (F(1,70) = 0.47, p = .73; log10 hair cortisol M ± SD, no discrimination= 4.84 ± 0.84, discrimination = 4.95 ± 0.78) patterns of association did not change when gestational age at birth was included in the univariate model, F(1,70)= 1.21, p = .28 (Table 4). However, greater experiences of perceived discrimination among pregnant individuals in the third trimester were associated with higher fetal hair cortisol levels in neonates (F(1,70) = 3.78, p = .03; log10 hair cortisol M ± SD, no discrimination = 4.44±0.51, discrimination = 4.71±0.51). This relation was no longer significant when gestational age at birth was included in the model, (F(1,70) = 0.94, p = .34; Table 4) and marginally significant when other covariates included (p=0.056).

Table 4.

Univariate Analyses for Study 2 (Border Town) to Compare Logged Neonatal Hair Cortisol Levels Between Fetal Exposure to Maternal Discrimination (n = 37) And No Exposure to Discrimination (n = 36).

	Model	Predictors	F	p
Early Pregnancy	1	Discrimination	0.475	.725
	2	Discrimination	1.211	.275
		Gestational age at birth	17.56	< .001***
	3	Discrimination	.911	.584
		Parity	.114	.705
	4	Discrimination	.875	.629
		Neonatal sex	1.429	.235
Late Pregnancy	1	Discrimination	3.783	.036*
	2	Discrimination	3.023	.078^
		Gestational age at birth	27.899	< .001***
	3	Discrimination	3.544	.056^
		Parity	.206	.651
	4	Discrimination	3.535	.056^
		Neonatal sex	.094	.760

Notes.

^{^}p < .10

^*p < .05

^**p < .01

^***p < .001.

2. Discussion

This study investigated the role of maternal discrimination in the programming of the fetal HPA-axis, as measured via hair cortisol. In the current study, neonatal hair cortisol was differentially associated with exposure to prenatal discrimination across the two cohorts. In study 1, US interior city, greater maternal reports of perceived discrimination were associated with lower neonatal hair cortisol. However, in study 2, US border town, more perceived discrimination was associated with higher neonatal hair cortisol levels, though only when gestational age was not included in the model. Importantly, both higher and lower levels of neonatal hair cortisol are related to adverse neonatal and child outcomes. Lower levels of cortisol in the third trimester have been linked with poor birth outcomes such as prematurity and low birthweight (Hoffman et al., 2017; Stoye et al., 2021), as well as long-term poorer cognitive function (Davis et al., 2017; Davis and Sandman, 2010). On the other hand, higher levels of neonatal cortisol have been linked to long-term deficits in gross motor function in children (Caparros-Gonzalez et al., 2019) and increasing disease risk until middle childhood (Karlen et al., 2015). This work highlights the experience of discrimination during pregnancy as a potential source of health disparities and the intergenerational transmission of the adverse effects of discrimination for the next generation.

Few studies have addressed the role of prenatal exposure to maternal discrimination on the developing fetal HPA axis, likely due to methodological restraints of fetal cortisol collection. One study showed an altered infant (3–6 months) salivary cortisol response based on preconception levels of maternal discrimination and early life adversity (Hendrix et al., 2022). Another study found that prenatal ethnic discrimination during pregnancy was associated with larger acute cortisol reactivity to a stressor in 6-week-old infants (Thayer and Kuzawa, 2015). However, results from both prior studies could be affected by exposures in the postpartum period. Using neonatal hair in the current study addresses this limitation as collection of hair at birth provides an index of fetal cortisol. Thus, the current study provides novel data investigating prenatal exposure to maternal discrimination and newborn hair as a non-invasive assessment of in utero cortisol exposure.

In the current study, the relation between discrimination and neonatal hair cortisol varied by location. Other studies have shown differences in experiences of maternal discrimination and maternal mental health based on setting (US border vs. interior US city; Non et al., 2022), citing differences in policies and histories of immigrant and discriminatory practices. For example, border cities in Southern California (study 2) have three times the Latinx neighborhood density than the interior city in Colorado (Liu & Painter, 2012) and a 10% higher population of non-White individuals overall (US Census Bureau). In addition, the border city is classified as a “continuous gateway” for immigrant populations and has been a more traditional destination with a history of community support and integration (Pastor et al., 2012). Even though Southern California has this history, there has been a 52% increase in hate crimes towards Latinx individuals between 2016–2017 (FitzGerald et al., 2019) and Latinx mothers have reported an increase in discrimination and mental health burden at the same time (Non et al., 2022). On the other hand, the interior city (Denver) is classified a “re-emerging gateway”, which refers to a recent uptick in immigrant population in the 21st century (Singer, 2015). Thus, it is possible these varying histories and racial makeups within the cities may account for differences in discriminatory experiences. Additionally, participant level differences may contribute to variations in discrimination experiences. In Study 1 which took place in a U.S. interior city, there was a greater racial/ethnic diversity, with a larger portion of women identifying as African American or multi-racial. African American women often report the highest levels of discrimination, while reports of discrimination vary widely in the Latinx population by skin color and generation status (Lopez, 2018; Noe-Bustamante, 2021). In Study 2, which took place in a U.S. border city, all the women were Latinx. Further in Study 1, Latinx women were more likely to be born in U.S., have completed a higher level of education and more acculturated than those in the U.S. border city. Overall more educated and more acculturated persons report more discrimination (Pérez et al., 2008). Taken together, using two different cohorts with varied experiences, the current study highlights discrimination experienced by pregnant individuals as an environmental exposure that potentially programs the developing fetal HPA axis.

Maternal discrimination during pregnancy has consistently been related to birth outcomes in marginalized populations (Larrabee Sonderlund et al., 2021; Liu et al., 2023a). Although few of these studies assess the developing HPA axis, preterm birth (Hollanders et al., 2017; Stoye et al., 2021) as well as low birthweight (Hoffman et al., 2017; Osterholm et al., 2012; Stoye et al., 2021) are both associated with altered cortisol patterns in infants. Thus, the pathways between birth outcomes and fetal HPA axis development are likely highly linked. For example, the fetal HPA axis is associated with maturation of vital organs and the central nervous system and has been shown to indirectly contribute to the timing of parturition (Austin and Leader, 2000; Ishimoto and Jaffe, 2011). Thus, the processes by which fetal exposure to maternal discrimination leads to adverse birth outcomes are likely linked to the development of the fetal HPA axis as well (Deer et al., 2024). It is not surprising then that gestational age at birth attenuated the relationships between maternal discrimination and neonatal hair levels in the current study. Discrimination has risen as a salient risk factor that may contribute towards racial/ethnic health disparities in length of gestation in African-Americans (Hilmert et al., 2014; Mendez et al., 2014) and the Latinx population, though inconsistently so (Dixon et al., 2012; Earnshaw et al., 2013; Liu, D’Anna-Hernandez, et al., 2023; Mendez et al., 2014). Other work that addresses sociocultural factors related to stress, such as acculturation, within the Latinx population were associated with both low birthweight and preterm birth mediated by maternal cortisol levels (D’Anna-Hernandez et al., 2012). In fact, lifetime discrimination may contribute to maternal stress (Gillespie et al., 2021; Knorr and Fox, 2024) and/or depression (D’Anna-Hernandez et al., 2015; Earnshaw et al., 2013; Fox, 2021; Noroña-Zhou et al., 2022) which itself is related to preterm birth (Glynn et al., 2008; Hoffman et al., 2016) and infant HPA activity (Davis et al., 2011). Future work should address the role of maternal mental health as a mediator and potential mechanism on the pathway between discrimination and infant cortisol. In the current study, maternal depression could not be evaluated as a mediator due to small sample size; however, taken together, this work suggests maternal discrimination has adverse effects on fetal HPA development with potential long-term consequences.

Findings should be considered in the context of several strengths and limitations. First, the assessment of neonatal hair to assess fetal cortisol exposure and production is a strength as much of the prior literature on fetal exposure to cortisol has used maternal cortisol as a proxy for the fetal experience (Khoury et al., 2023). The current study is the first to examine the association between discrimination and neonatal hair cortisol, which allows for a direct examination of cortisol accumulation in the third trimester. Second, the use of two diverse cohorts allows for the assessment of these relations across different environments (interior city and border town) that likely signify a wide diversity of experiences. However, the use of two different discrimination measures administered at differing gestational intervals limits comparisons across the two cohorts. In the interior city sample, the discrimination measure focused on everyday experiences of any type of discrimination (i.e., racial/ethnic, gender, disability status), whereas in the border city sample the measure focused on frequency and perception of everyday experiences of racial/ethnic discrimination. Thus, this work does limit our ability to make conclusions about the effects of specific types of discrimination, including intersecting identities, as those with multiple marginalized identities often have the worst mental health outcomes (Vargas et al., 2020). In addition, in Study 2, which was comprised of a Latinx only population in the border city, mothers are likely experiencing discrimination related to acculturative stress and/or legal status (Garcini et al., 2018; Preciado and D’Anna-Hernandez, 2017; Ratcliff et al., 2015) and should be addressed in future work. The measures were also administered at different times during pregnancy (mid vs. late) and previous relations between maternal stress and neonatal hair cortisol have varied depending on the timing and type of stress (Hollanders et al., 2017; Romero-Gonzalez et al., 2018; van der Voorn et al., 2018). These factors could account for the differing pattern of results documented in this paper. Given there is likely an indirect association between mother’s experiences of discrimination and neonatal hair cortisol, larger studies with greater sample size will be able to look mechanistic mediators to (i.e., maternal HPA axis and/or placental axis dysregulation) by which maternal experiences of discrimination may directly affect fetal development.

3.1. Conclusion

The current study points to prenatal experiences of maternal discrimination as an important contributor to fetal cortisol as measured in neonatal hair. As neonatal hair cortisol reflects cortisol of maternal origin as well as cortisol of fetal and amniotic fluid origin, this is a much more direct measure of the fetal experience than previous measures (Meyer & Novak, 2021). As such, this is the first study to examine the relation between fetal exposure to maternal discrimination and neonatal hair cortisol levels as a marker of fetal HPA axis development. Health disparities continue to exist in birth outcomes and the disruption of fetal development via exposures to maternal discriminatory experiences could be one process that contributes to the intergenerational transmission of stress. As the pathway between maternal experiences of discrimination and neonatal hair cortisol are unknown, it is possible that many different processes such as maternal HPA and placental axis dysregulation, health behaviors, shared genetic etiology, among other processes, could be underlying this association (Eilertsen et al., 2020; Rinne et al., 2022; Sandman et al., 2012). Future work should investigate these biological mechanisms to identify modifiable factors to ameliorate the adverse effect of discriminatory exposures on development of the fetal HPA axis.