Prenatal behavioral contagion through maternal yawning and fetal resonance

: Yawning is a phylogenetically preserved and highly stereotyped behavior observed across vertebrates.1 In humans, it emerges early in development, as it is already present prenatally.2,3 Qualitative studies show that fetal yawns display a structured motor pattern closely resembling adult yawns, suggesting a role in early sensorimotor organization,4,5 and they have been proposed to support the maturation of brainstem central pattern generators and early synaptic development.6,7 Due to its early emergence in development, prenatal yawning has largely been interpreted as driven by endogenous programs, whereas in postnatal life, yawning can also be shaped by the social context through contagion, a phenomenon linked to sensorimotor mirroring and affective attunement.8,9 Here, we tested whether prenatal yawning may also be modulated by maternal behavior. Using ultrasound recordings of fetal facial activity combined with controlled elicitation of maternal yawning, we show that fetal yawning selectively increases following maternal yawns but not during non-contagious control conditions. Temporal analyses reveal structured coordination between maternal and fetal yawning, and machine-learning classification identifies shared kinematic signatures across maternal and fetal yawns. These findings suggest that fetal yawning might also be embedded within a dyadic sensorimotor context in which maternal behavior shapes fetal expression, suggesting that forms of behavioral resonance and embodied alignment precede birth and contribute to the early foundations of social attunement.