Although fertility is reduced significantly in End Stage Renal Disease (ESRD), it is believed to improve after kidney transplantation. Due to homodynamic changes which occur during pregnancy, there is still concern about the impact of pregnancy on the outcome of kidney transplantation. In this study we surveyed this probable effect. In this historical cohort, we grouped female kidney recipients who were in their reproductive ages into Group I (n=86, pregnancy occurred) and Group II (n=125, pregnancy did not occur). Census sampling was done in Baqyiatallah hospital, Tehran, Iran, 1995-2002. The two groups were matched for age, cause of ESRD and treatment protocol. All the subjects had normal creatinine level (<1.5 mg/dl) on entry to our study. The subjects were followed for 45.4±22.05 and 46.38±19.84 months, respectively, in each group (p>0.05). Rise in the creatinine level (>1.5mg/dl) was considered as the main outcome measure. Mean (SD) age in Groups I and II were 26.6±6.6 and 26.9±8.1, respectively (p>0.05). In Group I, only in 9 (10.5%) subjects did the creatinine level rise, while in Group II, the serum creatinine level rose in 35 subjects (28%) (P=0.02). In this study we found that a lower number of subjects who became pregnant after kidney transplantation show an increase in their plasma creatinine level in comparison to the others. It may be secondary to the physiological immune suppression which happens during pregnancy.