Alteration in the time and/or mode of delivery differentially modulates early development in mice.

Delivery is a complex biological process involving hormonal and mechanical stimuli that together condition the survival and development of the fetus out of the womb. Accordingly, changes in the time or way of being born are associated with an alteration of fundamental biological functions and hypothesized to promote the emergence of neurodevelopmental disorders. Hence, the steadily rise in preterm birth and cesarean section (CS) delivery rates over the past years has become a worldwide health concern. In our previous work, we reported that even though no long-term autistic-like deficits were observed, mice born preterm by CS presented early transient neuronal and communicative defects. However, understanding if these alterations were due to an early birth combined with CS delivery, or if prematurity solely could lead to a similar outcome remained to be evaluated. Using mice born either at term or preterm by vaginal or CS delivery, we assessed early life ultrasonic vocalizations and the onset of eye opening. We report that alterations in communicative behaviors are finely attuned and specifically affected either by preterm birth or by the association between CS delivery and preterm birth in mice, while delayed onset of eye opening is due to prematurity. Moreover, our work further underlies a gender-dependent vulnerability to changes in the time and/or way of being born with distinct outcomes observed in males and females. Thus, our results shed light on the intricacy of birth alterations and might further explain the disparities reported in epidemiological studies.