Objective: The study aimed to evaluate the impact of prenatal maternal stress on birth weight using a large cohort of predominantly Caucasian women living in an urban area. Method:Women were recruited between 2005 and 2010. Data collection took place between the 24th and the 28th week of gestation. The Measure of Psychological Stress (MSP-9), a validated tool to assess stress symptoms, was used to collect data on prenatal maternal stress (independent variable). Birth weight (dependent variable) was classified as low birth weight (LBW; 2,500 g), normal birth weight (NBW; 2,500-4,000 g), and macrosomia (>4,000 g).Adjusted odd ratios (aOR) were obtained after performing multivariate logistic regressions adjusted for potential cofounders. At the final stage, 5,721 women were included in analysis.Results: When compared with women experiencing low stress, participants with high-stress scores were at increased risk of delivering an infant with LBW before adjustment [OR = 2.06, 95% CI (1.04-4.09)], but, after adjustment, only a nonsignificant trend remained. However, women experiencing intermediate and high levels of stress were at increased risk of delivering a baby with macrosomia, even after adjustment [aOR = 1.23 ; 95% CI (1.02-1.49)] and [aOR = 1.76 ; 95% CI (1.11-2.77)] compared to those who scored low on the psychological stress scale. Conclusion: Women exposed to high self-reported psychological stress during second trimester (24 th to 28 th weeks) of pregnancy have a 1.7-fold increased risk for delivering a baby with macrosomia when compared to women exposed to low psychological stress.

Birthweight is an important predictor of newborn health and has been linked to maternal psychological stress during pregnancy. However, it is unclear whether prenatal stress affects birthweight similarly for both male and female infants. We used a well-established pregnancy cohort to investigate the impact of high maternal psychological stress during pregnancy on birthweight as a function of infant sex. Overall, 5702 mother-newborn pairs were analysed. Of these, 198 mothers reported high levels of stress using the Psychological Stress Measure (nine-items version; PSM-9). Maternal psychological stress was assessed between the 24th and 28th week of gestation and analyses were performed jointly and independently as a function of neonatal sex (separate analyses for male and female infants). Newborns exposed to high maternal psychological stress during pregnancy (a score above 26 measured using the PSM-9 questionnaire, corresponding to >97.5th percentile) were compared to newborns of mothers who reported lower stress. ANCOVAs revealed that high levels of maternal stress during pregnancy were linked to infant birthweight as a function of infant sex. Male infants of mothers who reported high levels of stress had a greater birthweight whereas female infants had a lower birthweight under the same conditions, in comparison to mothers who did not report greater levels of stress. Although the effect size is small, these results underline the possibility that male and female fetuses may use different strategies when adapting to maternal adversity and highlight the need to consider infant sex as a moderator of the association between maternal psychological stress during pregnancy and infant birthweight.

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