Abstract Pregnant rats were exposed to an acute or a repeated stress (presence of a cat) either at the 10th or the 14th gestational day, and the development of their offspring was studied during the first 2 weeks of life. Motor development was measured by different tests: rooting reflex, vibrissae placing response, righting reflex, negative geotaxis. Other landmarks such as eye opening and spontaneous locomotor activity were also recorded. The results showed that, except for the rooting reflex which was most often enhanced (while not significantly) in prenatally stressed rats, the development of the vibrissae placing response, the righting reflex and the negative geotaxis behavior was delayed in the offspring of dams stressed at the 10th gestational day and not (or almost not) in the offspring of dams stressed at the 14th gestational day, the delay being more severe when the prenatal stress was repeated than when it was acutely administered. The spontaneous motor activity was also altered in repeatedly prenatally stressed rats, whatever the day of pregnancy when it was administered, while it was unaffected in acutely prenatally stressed animals. The delay in motor reflexes development was interpreted as alterations in maturation of nervous structures sustaining motor skills, while permanent decrease of spontaneous motor activity was explained by emotional and motivational alterations due to prenatal stress.