Plasma Oxytocin Concentrations During and After Gestation in Japanese Pregnant Women Affected by Anxiety Disorder and Endometriosis

Abstract

Background: Oxytocin has a key role in mother-infant bonding, maternal care, social interaction, and stress-related psychiatric disorders. However, the factors determining oxytocin concentrations during and after pregnancy such as medical history related to nursing or parental behavior are unknown. To elucidate these, we analyzed the relationships between oxytocin concentrations during and after pregnancy, and medical history assessed in the Japan Environment and Children's Study (JECS).

Methods: We then selected the pregnant women with a medical history of anxiety disorder and endometriosis as cases and pregnant women without medical history as controls adjusting the cohort for age and parity for a nested case-control study, after which 162 women remained for analysis. We evaluated 162 pregnant women from JECS using answers provided in a questionnaire and by measuring plasma oxytocin concentration by ELISA during the first (T1) and second (T2) trimesters of pregnancy, and after childbirth (T3).

Results: Oxytocin concentration increased in a time dependent manner, consistent with previous reports. There were weak negative correlations between oxytocin concentration at T1 and the mother's age and height, but no correlation with other factors. The mean oxytocin concentrations of pregnant women with a history of an anxiety disorder (n = 7) and endometriosis (n = 13) were significantly lower than those of pregnant women with no such history at T2 and T3.

Conclusion: These results suggest that oxytocin concentrations during and after pregnancy were affected by a past history of anxiety disorder and endometriosis. This is the first study of the relationship between oxytocin concentration and endometriosis. To elucidate the molecular mechanisms, further study is needed.

Keywords: anxiety disorder; endometriosis; oxytocin.

Fig. 1.

Time course of plasma oxytocin concentration in mothers. Plasma oxytocin increased during pregnancy in a time-dependent manner. Blood samples were collected during the first (15.7 ± 3.6 weeks of gestation, T1) and second (25.6 ± 2.0 weeks of gestation, T2) trimester of pregnancy, and after childbirth (3.4 ± 0.90 days postpartum, T3). Plasma samples were analyzed by ELISA. Values are mean ± SEM.

Fig. 2.

Time course of plasma oxytocin concentration in mothers with a medical history. Patients were classified by their medical history and their mean plasma oxytocin concentrations were calculated. Anxiety disorder (A) and endometriosis (B). Values are mean ± SEM. ***P < 0.001; *P < 0.05, by t-test.

Fig. 3.

Possible mechanism underlying the relationship between oxytocin concentration during pregnancy and medical history. (A) Basal oxytocin level was lower in mothers who had a history of an anxiety disorder. Due to inhibition of basal oxytocin secretion, an anxiety disorder developed. This inhibition affects the plasma oxytocin concentration during pregnancy. (B) Oxytocin receptor expression is affected by a maternal history of endometriosis. This change in expression affects the feedback from the uterus to the brain, resulting in lower plasma oxytocin during pregnancy.