Maternal Stress During Gestation: Birth Outcomes and the Stress-related Hormone Response of Neonates

Abstract

To the Editor, We read with great interest the article by Qian Su et al 1 , wherein they analyzed the effects of prenatal maternal stress on neonatal birth outcomes, neurobehavioral outcomes, and the stress-related hormone response of the neonates. The authors concluded that exposure to prenatal maternal stress results in negative outcomes in neonates. While we fully agree that the human fetus is sensitive to prenatal maternal stress, there are several issues that require further discussion concerning the interpretation of these study results. In this study, the Life Events Scale for Pregnant Women (LESPW), where events are weighted on the basis of different stressors, was used to assess maternal stress during gestation. Pregnant women with total scores >375 were assigned to the prenatal life-stressor-exposed group. However, detailed consideration of the LESPW revealed that this scale also included several positive life events that cannot be considered stressors. For example, reducing workload was weighted at 46, improving relationships with the family was 45, increasing revenue was 46, and being rewarded was 48. Considering these life events may overestimate the degree of maternal stress. Moreover, there are publications documenting the association between maternal positive emotions and more favorable birth outcomes. Effects of positive life events within the LESPW should be considered when interpreting the study results. As discussed in this article, one possible mechanism of maternal stress on fetal outcomes stems from decreased blood supply due to vasoconstriction associated with elevated norepinephrine and epinephrine levels. This study demonstrated that umbilical cord plasma norepinephrine and epinephrine levels were significantly higher in the prenatal life-stressor-exposed group. However, the LESPW score was collected before delivery, and the aforementioned stress-related hormones from cord blood were collected immediately after delivery. It is, therefore, possible that the levels of norepinephrine and epinephrine reflected, in part, acute stress during labor rather than maternal stress during gestation. Furthermore, causal relationships were unclear in this study due to a lack of reporting of maternal levels of these hormones. Moreover, the study would be more convincing had it included direct evidence, such as Doppler ultrasound assessment of the umbilical and uterine arteries. The topic of this study was very interesting, and the effect of maternal stress on neonatal outcomes is an important issue; however, a more comprehensive tool for the assessment of maternal stress and a more complete dataset are required before reaching conclusions. Conflicts of interest