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Objective: To investigate whether allogeneic uterine grafts in a rat model, with tacrolimus immunosuppression, can harbor pregnancies that result in offspring with normal postnatal growth. Design: Experimental animal study. Settingg: University hospital. Animals(s): Lewis rats as uterus donors and Piebald-Virol-Glaxo rats as recipients. Intrvention(s): Animals were allocated to one of the following three groups: allogeneic uterus transplantation with end-to-side anastomosis to the external iliac vessels and immunosuppression with tacrolimus (UT+Tac; n = 10); sham surgery and immunosuppression with tacrolimus (Sham+Tac; n = 10); or sham surgery (Sham; n = 10). The rats were subsequently introduced to male rats with proven fertility and in the event of resulting pregnancy cesarean sections were performed on day 22 of pregnancy. Main outcome measure(s): Graft viability, fertility rate, perinatal death, birth weight, postnatal birth trajectory. Results(s): Pregnancy rate was higher in the control groups (70% Sham and 80% Sham+Tac) than in the transplanted group (50% UT+Tac), although these differences did not reach the significance threshold. There were no differences between groups regarding number of living pups or neonatal deaths. Pups born from UT+Tac mothers had birth weights similar to external control animals from our breeding colony (BC): UT+Tac males 6.2 +/- 0.2 g, UT+Tac females 5.5 +/- 0.6 g, BC males 5.8 +/- 0.2 g, BC females 5.2 +/- 0.3 g; n.s. Evaluation of uteri and placentas of pregnant animals revealed a somewhat reduced vascular density in both tissues in the UT+Tac group, and that was not seen in the Sham+Tac group. Conclusion(s): Allogeneic uterus transplantation and immunosuppression with tacrolimus is compatible with normal pregnancy and perinatal outcome in a rat model. (C)2014 by American Society for Reproductive Medicine.