Abstract:
Stress during pregnancy can adversely affect fetal and neonatal development, as well as increase the risk of obesity, type 2 diabetes, or psychiatric disorders in later life. Moreover, several studies have already shown that both an increased body mass index (BMI) and increased inflammatory markers such as Interleukin-6 can have adverse effects on the development of the child. To prevent stress, relaxation techniques in particular have gained importance during pregnancy. Due to potential physical limitations in the third trimester of pregnancy, mental techniques are particularly well suited. In particular, listening to music during pregnancy has been shown to have a positive influence on the stress level of the pregnant woman. The aim of this work is to investigate the extent to which stress in pregnancy influences the maternal inflammatory milieu and the fetal autonomic nervous system. In addition, it will be investigated which relaxation technique (music, guided imagery or rest) has the greatest possible relaxation effect as measured by the maternal autonomic nervous system. Three different studies were conducted as part of this work: The first study deals with two mental relaxation techniques (music and guided imagery). The aim was to investigate which of the two relaxation techniques compared to a control group (no relaxation stimulation) relaxes pregnant women between the 30th and 40th week of pregnancy the most. Here, maternal heart rate, maternal skin conductance and general stress level of the subjects were measured. In this study, no significant difference between the relaxation groups was determined. All three relaxation groups showed a significant improvement in maternal stress level on basis of the questionnaires and a Visual Analog Scale. In the second study, we compared the effect of acute mental relaxation (listening to music) on the maternal and fetal autonomic nervous system of pregnant women in comparison to a control group (no relaxation stimulation). The extent to which chronic stress of the mother influences the fetal autonomic nervous system was also investigated. Maternal and fetal cardiovascular activity was recorded using fetal magnetoencephalography (fMEG), during which maternal skin conductance level was also measured. To investigate the influence of chronic stress, hair samples and blood samples were taken from the subjects. We could not detect any significant difference in maternal relaxation between the groups on the basis of the physiological parameters. However, we showed significantly different changes of fetal heart rates. In addition, no significant effect of maternal chronic stress (hair cortisol) on the changes in fetal heart rate were observed. Based on the questionnaires, we investigated a significant correlation between chronic stress and the change of fetal heart rate variability. The third study investigated the effects of maternal stress in pregnancy on the inflammatory milieu as well as insulin sensitivity in pregnant women. In three stress groups (no stress, low stress, mild stress), we did not detect any significant difference in the level of Interleukin-6, an inflammatory marker, between the groups. However, in our cohort, we found a significant association between pre-pregnancy BMI and Interleukin-6. Interleukin-6 and maternal insulin sensitivity as well as women's cortisol levels correlated significantly with each other. We used mediation analysis to demonstrate that increased pre-pregnancy BMI associated with maternal stress in pregnancy had a significant influence on the Interleukin-6 level. Overall, on the basis of the three studies performed, we demonstrated that maternal mild stress had no effect on the maternal inflammatory milieu. However, the combination of increased pre-pregnancy BMI, decreased insulin sensitivity and mild stress during pregnancy resulted in a disbalance in the inflammatory milieu. With regard to chronic stress, we detected influence on fetal heart rate variability only. Focusing on relaxation, we demonstrated that maternal relaxation has a significant positive influence on the well-being of the mother but not on the fetal nervous system. On the basis of these studies, the phase prior to pregnancy in particular comes into focus, both with regard to an increased BMI before pregnancy and stress-reducing measures during pregnancy. Here, especially through structural stress screening at the beginning of pregnancy, women with high chronic stress could be supported at an early stage and stress management interventions could be developed and offered.
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