Background and Purpose
Adverse birth outcomes such as preterm birth and low birth weight threaten both children’s survival and their long term health. Current evidence suggests a potential link between stress during pregnancy and adverse birth outcomes. Some research suggests that high maternal perceived stress may shorten the length of gestation, and increase the risk of an infant being small for gestational age or low birth weight. However, findings are not consistent across studies. In addition, it is not clear whether perceived stress or biological measures of stress (such as cortisol) may best predict stress-related birth outcomes and whether these relationships are moderated by sex of the fetus. Lastly, research is not clear on whether perceived stress and cortisol are associated with one another or may represent uniquely different components of the stress response. The overall purpose of this study was to clarify the relationship between perceived stress and cortisol values, their roles as predictors of infant birthweight or gestational age, and the moderating role of fetal sex on stress-related birth outcomes.
Methods
The sample included 58 women who were recruited in obstetric clinics during their third trimester of pregnancy. They ranged in age from 23 to 47 years. Women completed Cohen’s Perceived Stress Scale and provided 8 saliva samples across 2 days between 26 and 40 weeks gestation. Salivary samples were used to determine average cortisol level, cortisol awakening response (CAR), diurnal slope, and total cortisol excreted throughout the day (AUCG). Electronic medical records were used to derive a measure of perinatal risk and acquire data on infant gestational age, weight, and sex at birth. Correlation coefficients were used to determine relationships between perceived stress and the 4 cortisol parameters. Logistic regression models were computed to determine the odds of infants being born preterm or low birth weight as a result of their mothers’ self-reported stress and cortisol parameters. The moderating role of fetal sex was also examined in these models.
Results
On average, women reported a moderate amount of perceived stress. For the total sample, women’s perceived stress was not related to any cortisol parameters. However, women who were ≤29 weeks of gestation in their pregnancy showed opposite and stronger associations between perceived stress and their mean cortisol level, cortisol awakening response, and AUCG than did women who were ≥30 weeks of gestation when assessed. Perceived stress had no relationship to either low birth weight or preterm birth. One cortisol parameter did show a significant effect on birth outcome, but was moderated by fetal sex. Male infants whose mothers had higher salivary CAR during the third trimester of pregnancy had greater odds of being born low birth weight.
Conclusion
Findings indicate the need for further research on cortisol response at different pregnancy stages, as well as inclusion of self-report and different cortisol parameters when assessing stress. Results also suggest that a woman’s elevated CAR during the 3rd trimester could serve as an indicator of risk for low birth weight male infants. Further research is needed to replicate these findings in a larger sample that has more heterogeneity and the power to examine moderating effects of fetal sex. If future findings support the role of CAR in predicting risk, salivary CAR sampling could be a valuable method to assist in mitigating women’s risk for delivering an infant of low birth weight and related morbidities.
