Markers of the maternal oxytocin system and mother-infant bonding during the first postpartum year

The oxytocinergic system is central to early mother-infant bonding, yet, its epigenetic and hormonal dynamics during the postpartum period are not well understood. The aim of this study was to investigate genetic, epigenetic, and endogenous markers of the oxytocinergic system in relation to mother-infant bonding during the first year postpartum.

A sample of 66 mothers (mean age = 32.0 years, SD = 3.6 years) with bonding problems (N = 36) undergoing a neurofeedback intervention and control mothers (N = 30) participated in this longitudinal randomized clinical trial. We measured DNA methylation (DNAm) of the oxytocin gene (OXT), the oxytocin receptor gene (OXTR), and the Cluster of Differentiation 38 (CD38) gene in peripheral blood cells collected at three, six, and 12 months postpartum. At the same timepoints, mothers completed questionnaires on maternal bonding, depressive symptoms, and maternal self-confidence. Furthermore, they provided blood samples to assess endogenous oxytocin (OT) and three OXTR single-nucleotide polymorphisms. Data was analyzed using multilevel models.

We found no case-control differences or associations of bonding indicators or OT with DNAm at baseline and across time. OXT, but not OXTR DNAm changed significantly over time independent of group or intervention. For OT, we found a significant time by intervention interaction with decreasing OT levels in the intervention groups.

We found limited evidence for an association between oxytocin biomarkers and maternal bonding problems. However, changes in OXT DNAm and treatment-specific changes in OT during the first year postpartum might indicate some maternal adaptation in the maternal oxytocinergic system.