maternal viral mimetic administration at the beginning of fetal hypothalamic nuclei development accelerates puberty in female rat offspring this study aimed to investigate the effects of maternal viral infection during a critical time window of fetal hypothalamic development on timing of puberty in the female offspring for that purpose a viral mimetic ie synthetic doublestrand rna namely polyinosinicpolycytidylic acid poly ic or saline was injected ip to the pregnant rats during the beginning day 12 of pregnancy n 5 for each group or at the end of this time window day 14 of pregnancy n 5 for each group four study groups were formed from the female pups n 910 pupsgroup following weaning of pups vaginal opening and vaginal smearing was studied daily until 2 sequential estrous cycles were observed during the second diestrus phase blood samples were taken for progesterone leptin corticosterone folliclestimulating hormone and luteinizing hormone maternal poly ic injection on day 12 of pregnancy increased body mass and reduced the time to puberty in the female offspring neither poly ic nor timing of injection affected other parameters studied p 005 it has been shown for the first time that maternal viral infection during the beginning of fetal hypothalamic development might hasten puberty by increasing body mass in rat offspring