The impact of labor induction in vaginal delivery on the development of mother-to-infant bonding and the mediating role of breastfeeding practices: the Japan Environment and Children's Study.

PURPOSE: Labor induction using medications such as synthetic oxytocin (synOT) and prostaglandins (PG) has become increasingly common; however, its implications for mother-to-infant bonding remain unclear. These agents may plausibly influence early bonding by altering peripartum oxytocin-related physiology and by affecting early breastfeeding establishment. We examined whether labor induction and specific induction agents are associated with postpartum mother-to-infant bonding trajectories and evaluated breastfeeding mode as a potential mediator.

METHODS

We analyzed data from the Japan Environment and Children's Study (JECS). Among 104,059 fetal records, we included 58,384 mother-infant dyads with complete bonding data at 1, 6, and 12 months postpartum (56.1%; complete-case analysis), restricted to liveborn, term, singleton vaginal deliveries. Mother-to-infant bonding was assessed as mothers' self-reported bonding-related feelings using the Mother-to-Infant Bonding Scale (MIBS). Induction status and induction agents (synOT, PG) were obtained from transcribed medical records. Linear mixed-effects models tested associations with bonding trajectories, and mediation analyses evaluated whether 1-month feeding mode (exclusive formula vs. any breastfeeding) accounted for observed associations.

RESULTS

Induction was associated with a time-varying pattern in mother-to-infant bonding (time × induction: β = -0.057, 95% CI [-0.067, -0.046], p < 0.001), although contrasts at 1, 6, and 12 months were not significant (β = 0.013, p = 0.109; β = 0.005, p = 0.482; β = 0.000, p = 0.953). SynOT was associated with poorer bonding at 1 and 6 months (β = 0.027, p = 0.004; β = 0.016, p = 0.024), but not at 12 months (β = 0.010, p = 0.205). Mediation via feeding was small for induction (indirect effect = 0.001, 95% CI [0.0002, 0.001]) and not supported for synOT (indirect effect = 0.0004, 95% CI [-0.00009, 0.001]).

CONCLUSION

Labor induction and synOT exposure were associated with poorer early postpartum mother-to-infant bonding, with differences attenuating over the first postpartum year. Exclusive formula feeding was associated with poorer bonding and may contribute to early postpartum differences, supporting the clinical value of proactive breastfeeding support and attention to maternal wellbeing while reassuring families that early challenges often ease over time.