Objective   To investigate the effect of pregnancy on fracture healing of rabbit.    Methods   A total of 30 pregnant Japanese big ears white female rabbits and 30 matched female rabbits were subjected. Fracture model was established in 9 d after pregnancy. Before

and 1

2

and 3 weeks after model establishment

their blood was extracted and stored at -80 ℃ for growth hormone with radioimmunoassay. Callus samples were collected for morphological and immunohistochemical study. Computed radiography (CR) was performed for radiological data.    Results   Serum growth hormone in pregnant group was 1.331±0.067

1.426±0.024

1.507±0.109 and 1.826±0.289 ng/ml respectively in 0

1

2 and 3 weeks of model establishment

significantly higher than those in control group except for the time of model establishment (1.208±0.151

P0.05; 1.317±0.102

1.246±0.192 and 1.340±0.313 ng/ml for the 3 time points

P0.05). There was more bone morphogenetic protein (BMP) expressed in the callus of pregnant group than in that of the control (P0.05). CR indicated that more condensed callus was observed in the pregnant group than in the control (P0.05).    Conclusion   Pregnancy in early metaphase promotes fracture healing in rabbits.