Abstract: OBJECTIVE： To investigate effects of serum thymic factors on the growth and development， learning ability and reproductive ability of rats during the late pregnancy，delivery，lactation；as well as during postnatal periods of embryos and fetuses. METHODS：After successful mating，female SD rats were into 20 in each group. From the 15th day of pregnancy to the end of the lactation period， serum thymus factors were administered by continuous subcutaneous injection at 0.88，1.75 and 3.50 mg/kg respectively，and 0.9% chloride was provided. Sodium injection was the solvent control group. The body weight and food intake of the F0 generation female mice were regularly weighed；the birth survival rate and lactation survival rate of F1 generation offspring mice were determined，and the physiological development and neonatal reflexes reach the standard age， and the learning and memory abilities were trained. The reproductive behavior of the offspring after mating in the ¹²th week after birth was observed， and the various indicators of embryotoxicity was determined. RESULTS： After injection of serum thymic factors，the average body weight and food intake of the F0 generation pregnant and lactating mice in the solvent control group and the test drug groups were normal at each week，and the total number of offspring，sex ratio and birth survival rate (96.3%-97.9%) and the survival rate during lactation (97.7%-98.9%) were basically consistent. The average body weight and food intake of F1 generation mice during lactation and after weaning were basically normal. The physiological development and neonatal reflex time point examination items of the offspring in the solvent control group were all normal at the standard age，swimming adaptation time (28.5±15.8) s，spatial positioning establishment time (134.9±44.1) s，and darkroom electric shock reflex establishment time (4.9±3.1) s，the number of electric shocks to establish memory is 1.7±0.9；the cage mating rate of F1 generation sexually mature rats in the solvent control group was 100%，the pregnancy rate was 90%，the average number of implantations was 10.6±2.1，and the average number of live fetuses was 10.2±1.9， the number of stillbirths was 3，and the number of malformed fetuses was 1. The above indicators did not show significant changes in each dose group of the tested drug. Compared with the solvent control group， the differences were not statistically significant. CONCLUSION：Under the conditions of this experiment，no obvious abnormalities were found in the growth and development，neurobehavior，and reproductive ability of rats in late pregnancy and F1 generation embryos and fetuses in the three dose groups of the solvent control group and serum thymus factor，and no perinatal toxicity was found.

Key words: serum thymic factor, rat, pups, growth and development, reproductive toxicity