Infant Stimulation Induced a Rapid Increase in Maternal Salivary Oxytocin

Abstract

Oxytocin (OT) is a neuropeptide involved in human social behaviors and reproduction. Non-invasive OT levels in saliva have recently roused interest as it does not require a specialized medical setting. Here, we observed one woman's basal serum and saliva OT from pregnancy to 1 year postpartum to track OT concentration changes over this period. We examined the changes in salivary OT levels over time in response to maternal physiological and behavioral responses. The fluctuation of saliva OT levels is well correlated with serum OT during pregnancy and breastfeeding. However, while salivary OT increased rapidly during direct interaction (social interaction tests) with the infant and/or when the mother was watching her own infant's video (video tests), no increase was observed in serum. We used social interaction and video tests on a group of mothers (nine mothers for social interaction and six for the video test) to clarify these single-subject results. In both tests, the mothers had increased OT in their saliva but not serum. Our study may suggest that salivary samples reflect not only the physical but also the emotional state and that saliva samples may be useful for monitoring women's OT levels during pre- and postpartum periods. Further studies with larger sample numbers are necessary to confirm the rapid changes in salivary OT levels in response to maternal physiological and behavioral responses.

Keywords: breastfeeding; labor; mother-infant interaction; oxytocin; perinatal period; pregnancy; saliva; serum.

Figure 1

Changes in salivary and serum oxytocin (OT) from early pregnancy to the labor of one woman. (A) Salivary and serum OT concentrations from gestation weeks 6 to 40. (B) Salivary and serum OT concentrations in the first stage of labor.

Figure 2

Changes in salivary and serum oxytocin (OT) concentrations during breastfeeding in one woman. (A) The time course of experiments. Samples were collected before (basal), 5, and 10 min after initiation of breastfeeding, and 30 min after feeding ended. Values were averaged from samples taken on postpartum days 1, 3, 5, 7, 30, and 90. (B) Salivary OT concentration. (C) Serum OT concentration. The experiment was repeated six times with one mother (n = 6). The values are the mean ± SEM. OT: oxytocin. One-way repeated measures ANOVA (d.f. = 3; * p < 0.05 ** p < 0.01).

Figure 3

The trajectory of salivary and serum oxytocin (OT) concentrations from early pregnancy to 90 days postpartum of one woman. (A) The concentration of salivary and serum OT levels from 6 weeks gestation to 90 days postpartum. The basal OT concentration from the measurement of breastfeeding experiments was used for values of postnatal days. The value in the intermittent period of first stage labor was used for plotting the time point of labor (value at cervical opening 3). (B) The trajectory of relative changes of salivary and serum OT levels from 6 weeks gestation to 90 days postpartum. (C) Correlation between salivary and serum OT concentrations from early pregnancy to postpartum day 90. Note that OT concentrations from every time point of all postnatal breastfeeding experiments were plotted.

Figure 4

Changes in saliva and serum oxytocin (OT) concentrations during the direct mother-infant interaction test of one woman. (A) Schematic procedure of the interaction test. (B) Saliva OT concentration. (C) Relative changes in salivary OT. (D) Serum OT concentration. (E) Relative change in serum OT. The experiment was repeated six times with one mother (n = 6). Values are the means of six repeated experiments and are the means ± SEM; one-way repeated measures ANOVA (d.f. = 8; * p < 0.05).

Figure 5

Changes in salivary and serum oxytocin (OT) concentrations of one woman while watching the video of the infant or reading a newspaper. (A and B) The time course of the video (A) and newspaper-reading experiments (B). (C) Salivary and serum OT concentrations while watching the video. (D) Relative changes in salivary and serum OT concentrations while watching the video. (E) Salivary and serum OT concentrations while reading a newspaper. (F) Relative changes in salivary and serum OT concentrations while reading a newspaper. The experiment was repeated six times with one mother (n = 6). Values were averaged across six repeated experiments, respectively. Values are the mean ± SEM; one-way repeated measures ANOVA (d.f. = 7; * p < 0.05).

Figure 6

Changes in salivary and serum oxytocin (OT) concentrations of a group of mothers. (A) Schematic procedure of the direct mother-infant social interaction, video-watching, and reading tests. (B) Salivary and serum OT level during the direct mother-infant social interaction test. (C) Relative change in salivary and serum OT during the direct mother-infant interaction test. (D) Salivary and serum OT level while watching the video of the infants. (E) Relative change in salivary and serum OT while watching the video of the infants. (F) Salivary OT level while reading a newspaper or a book. (G) Relative change in salivary OT while reading a newspaper or a book. Nine participants took part in the direct mother-infant interaction test, and six of these took part in the video and newspaper or book reading test. Values are given as the means ± SEM; one-way repeated measures ANOVA (d.f. = 9, interaction test; d.f. = 7, video and reading test; * p < 0.05, ** p < 0.01).