Summary: New research reveals that the timing of stress during pregnancy has gender-specific effects on infants, altering how boys and girls respond to stress differently. Scientists found mid-pregnancy stress has a stronger impact on girls’ stress reactivity, while boys are more sensitive to stress experienced in late gestation.
The study involved analyzing infants’ hormonal responses to mild stress and temperament after prenatal stress exposure, correcting previous beliefs that girls were generally more sensitive. These findings emphasize the importance of considering the timing of prenatal stress exposure to understand and possibly mitigate long-term mental health risks.
Key Facts:
- Timing Matters: Mid and late pregnancy are critical periods when prenatal stress differently influences boys and girls.
- Gender Differences: Boys showed greater sensitivity to stress later in pregnancy, correcting the misconception that prenatal stress primarily affects girls.
- Infant Stress Indicators: Researchers measured infants’ stress responses via cortisol levels after mild lab-induced stress and observed differences based on prenatal stress timing.
Source: Michigan State University
A team of researchers at Michigan State University and the University of Michigan found new insights on the timing of prenatal stress and its effect on infant stress reactivity and temperament — including differences between genders.
The study, published in Psychoneuroendocrinology, is the first to examine weekly stress across 27 weeks of pregnancy to pinpoint when it most affects a newborn’s stress response and temperament — two measures that indicate infant biobehavioral reactivity.
“Prenatal stress has a well-established link to negative health, including mental health, outcomes in children and adults, but most studies conclude that the biggest effects are on girls. Our study found that not to be the case. It’s in fact, just different timing,” said Alytia Levendosky, lead investigator of the study and professor in MSU’s Department of Psychology.
The researchers recruited 396 pregnant women, specifically from a high stress-risk population due to low income and/or exposure to intimate partner violence. Weekly stress assessments were conducted via email or text from week 15 through week 41 of pregnancy.
At six months postpartum, infant cortisol levels were collected before and after a mildly stressful laboratory task to see how their hypothalamic-pituitary-adrenal system, or HPA axis, responded to stress. Mothers also reported on infant temperament.
The study found periods of higher sensitivity to stress in both mid and late gestation but found that girls and boys had differing patterns of sensitivity. The data showed that experiencing stress in mid-gestation affected girls’ HPA axis and temperament, while late gestation stress impacted boys.
Previous studies in this field stopped their last stress assessment between 32-34 weeks. Because this study ran through week 41, Levendosky and her team were able to locate the time that was most sensitive for boys.
“This study is an essential step in correcting our understanding around prenatal stress effects for boys and girls,” said Joseph Lonstein, investigator on the study and professor in MSU’s Department of Psychology.
“We hope that our findings inspire additional research so we can better understand what is happening in fetal brain development across pregnancy and how it is affected by stress.”
Current funding allows the team of researchers to continue following these participants until the age of four — with assessments at 2.5 years old and again at 4 years old. Amy Nuttall, co-author of this study and associate professor in the Department of Human Development and Family Studies at MSU, hopes to continue the study through even later childhood.
About this stress and neurodevelopment research news
Author: Jack Harrison
Source: Michigan State University
Contact: Jack Harrison – Michigan State University
Image: The image is credited to Neuroscience News
Original Research: Open access.
“Pinpointing the timing of prenatal stress associated with infant biobehavioral reactivity” by Alytia Levendosky et al. Psychoneuroendocrinology
Abstract
Pinpointing the timing of prenatal stress associated with infant biobehavioral reactivity
Prenatal stress has a well-established link to negative biobehavioral outcomes in young children, particularly for girls, but the specific timing during gestation of these associations remains unknown.
In the current study, we examined differential effects of timing of prenatal stress on two infant biobehavioral outcomes [i.e., hypothalamic-pituitary-adrenal (HPA) axis reactivity and difficult temperament] that are early-life precursors to the development of psychopathology.
We obtained the most granular assessment of prenatal stress to date involving weekly stress ratings from 396 pregnant women between 15 and 41 weeks gestation. At 6 months postpartum, infant salivary cortisol was collected (n = 173) before and after a stressful laboratory task and mothers reported on infant temperament (n = 244).
Machine learning explored both between- and within-person regression effects of prenatal stress on the two infant biobehavioral outcomes.
For HPA axis reactivity, we found a sensitive period during mid-gestation (weeks 20 and 29) for girls, but during late gestation (week 37) for boys.
For difficult temperament, we found a between-persons effect of mean stress level as well as sensitive periods in mid (weeks 20, 21, 25) and late gestation (week 37) for girls, but across mid to late gestation (weeks 25, 27, 30, 34, 40) for boys.
This study is the first to use a weekly assessment across gestation to demonstrate specific windows of sensitivity for infant biobehavioral precursors of child psychopathology.
The findings highlight that biological sex critically influences specific timing of these prenatal stress associations with infant outcomes, thus informing our understanding of sex differences in early biobehavioral markers of psychopathology.
