High prolactin during pregnancy, which is essential for normal postpartum maternal behavior, increases neurogenesis in the subventricular zone of the lateral ventricle (SVZ) of the maternal brain.Since SVZ neurogenesis generates new olfactory neurons and may contribute to perception of novel odorants, we hypothesized that the prolactin-induced increase in SVZ neurogenesis during pregnancy might be important for normal maternal interactions with pups.To investigate this hypothesis, prolactin secretion was suppressed for three days early in pregnancy in mice, either pharmacologically using a carefully timed dose of bromocriptine, or physiologically using pheromone-containing urine-soaked bedding from an unknown female.