Oxytocin in the Circadian Timing of Birth

Background. The molecular components determining the timing for birth remain an incompletely characterized aspect of reproduction, with important conceptual and therapeutic ramifications for management of preterm, post-term and arrested labor. Methodology/Principal Findings. To test the hypothesis that oxytocin mediates circadian regulation of birth, we evaluated parturition timing following shifts in light cycles in oxytocin (OT)-deficient mice. We find that, in contrast to wild type mice that do not shift the timing of birth following a 6-h advance or delay in the light cycle, OT-deficient mice delivered at random times of day. Moreover, shifts in the light-dark cycle of gravid wild type mice have little impact on the pattern of circadian oxytocin release. Conclusions/Significance. Our results demonstrate oxytocin plays a critical role in minimizing labor disruption due to circadian clock resetting.