Pediatrics and Neonatology (2015) 56, 365e366
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EDITORIAL
Effects of Maternal Stress During Pregnancy on Birth Outcome and Stress-related Hormones The human fetus is exquisitely sensitive to physiological and psychological maternal stress. Prenatal stress can influence birth outcomes and impair neurobehavioral development of affected infants.1 Newborn infants who are exposed to prenatal maternal stress are associated with low birth weight, lower birth weight, and smaller head circumference.2 Studies also show that prenatal maternal stress disrupts cognitive performance and decreases brain volume, which are associated with learning and memory.3 There are also a number of reports linking maternal stress or antenatal anxiety to the appearance of emotional problems, hyperactivity, attention deficits, and Tourette’s syndrome in children.2 A growing body of literature documents associations of maternal psychosocial stress during pregnancy with fetal, infant, and child behavior and development. However, findings across studies are often inconsistent, which may in part be due to differences in stress definitions and assessments.4 Timing of prenatal exposure is important, however, few studies are available to determine the influence of the timing of prenatal exposure on physical and cognitive outcomes. In this issue of Pediatrics and Neonatology, Su et al5 reported that newborn infants exposed to prenatal life stressors had significantly lower birth weight, smaller birth head circumference, and lower scores of Neonatal Behavioral Neurological Assessment. Cord plasma adrenocorticotropic hormone, norepinephrine, and epinephrine levels were significantly increased but cortisol levels were decreased. There were some limitations in this study. Maternal life stressors during pregnancy were evaluated using the Life Events Scale for Pregnant Women before delivery. Neurobehavioral outcomes of infants were evaluated using the Neonatal Behavioral Neurological Assessment at 3 days of age in this study. Not only was recall bias inevitable but it was also difficult to address the sensitive time in gestation for the influence of prenatal stress. In terms of effects of prenatal maternal stress on neonatal neurobehavioral outcome, long-term follow up using different methods is recommended. This is important when
interpreting these data and comparing the results with other studies. Little is understood about the mechanisms that may underlie fetal programming by prenatal stress in humans. Maternal hypothalamicepituitaryeadrenal axis is one of the systems involved.6 Increased exposure of the fetus to cortisol can occur through increases in maternal cortisol associated with periods of stress, which then crosses the placenta into the fetal environment. However, the maternal hypothalamicepituitaryeadrenal axis becomes gradually less responsive to stress as pregnancy progresses, and there may only be a weak association between maternal stress and cortisol level, especially later in the pregnancy.6 Another proposed mechanism is that fetal programming may be partially mediated by cortisol without increasing maternal levels. The barrier enzyme, 11b-hydroxysteroid dehydrogenase type II (11bHSD2) of the placenta converts cortisol to inactive cortisone and protects the fetus from maternal cortisol. Previous studies also showed that prenatal stress could downregulate placental 11b-HSD2. Finally, the role of alterations in placental serotonin and the role of epigenetic changes may underlie many of the processes of fetal programming.7 The study conducted by Su et al5 did not measure maternal stress-related hormones. The decreased cord plasma cortisol level and elevated adrenocorticotropic hormone level in infants exposed to prenatal maternal stress was speculated to be consistent with adrenal hyporesponsivity, which occurs under conditions of chronic stress and downregulation of adrenal receptors as well as hypocortisolism. However, the reduced cortisol response might also result from the downregulation of 11b-HSD2 or the diurnal rhythm in the adrenocortical response. This study provides information on birth outcomes and short-term neurobehavioral outcomes, as well as the stressrelated hormone response of the neonates exposed to prenatal maternal stress. Future directions of research in this field are suggested to focus more on the sensitive time in gestation, intervention to reduce maternal stress, and the long-term follow-up outcome.
http://dx.doi.org/10.1016/j.pedneo.2015.08.004 1875-9572/Copyright ª 2015, Taiwan Pediatric Association. Published by Elsevier Taiwan LLC. All rights reserved.
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Editorial
Conflicts of interest The author indicates no potential conflicts of interest.
2.
Ming-Chou Chiang* Department of Pediatrics, Chang Gung Memorial Hospital, Taoyuan, Taiwan
3.
Graduate Institute of Clinical Medical Sciences, Chang Gung University College of Medicine, Taoyuan, Taiwan * Division of Neonatology, Department of Pediatrics, Chang Gung Memorial Hospital, 5e7, Fu-Shin Street, Guishan District, Taoyuan City 33305, Taiwan. E-mail address:
[email protected] Aug 14, 2015
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