Embryonic/fetal mortality after exposure to tritiated water in pregnant Swiss albino mice during different gestation periods.

Pregnant Swiss albino mice were given a priming injection(im) of tritiated water (HTO) at the dose rate of 2.3 and 5 microCi/ml body water (74, 111 or 185 KBq/ml body water) at 0, 6 and 14 day post conception (d.p.c.) and were subsequently maintained on tritiated drinking water ad libitum during preimplantation (0-5 d.p.c.), organogenetic (6-12 d.p.c.) or fetal (14-18 d.p.c.) period, respectively. On day 18 of gestation the females were sacrificed by cervical dislocation to record the implant sites per dam and embryonic/fetal mortality. Significant reduction was observed in average implant sites per dam when the females were exposed to any of the three doses during the preimplantation period due to embryonic resorption before implantation. However, the same was found to be within the normal range when mothers were exposed during the organogenetic or fetal period. Prenatal mortality (embryonic resorption/fetal death) was higher after in utero exposure to different doses during preimplantation period as compared to organogenetic period, but mortality did not occur after exposure to any of the doses during the fetal period. Occurrence of mortality was found to be dose dependent.