Oxytocin, a hormone already known for its role in childbirth, milk release, and mother-infant bonding, may have a newfound purpose in mammalian reproduction. In times of maternal stress, the hormone can delay an embryo’s development for days to weeks after conception, a new study in rodents shows. According to the authors, the findings about so-called ‘diapause’ may offer new insights into pregnancy and fertility issues faced by humans.