Background/Aim: This study aimed to explore the causes, incidence and outcome of renal insufficiency during pregnancy. Methods: All pregnant women admitted to our hospital from September 2004 to August 2007 were retrospectively screened for renal function. Patients were divided into 3 groups according to the serum creatinine (Scr) level (mild renal insufficiency: Scr 70-123 μmol/l; moderate: Scr 124-220 μmol/l; severe: Scr >221 μmol/l). Results: Seventy-five cases (2.51%) of renal insufficiency were identified. Twenty-two cases (0.73%) had evidence of chronic kidney disease before pregnancy. Compared to the moderate and severe groups, the mild group had the lowest blood pressure. In 29 recorded cases with multiple observations throughout pregnancy, the deterioration of renal function progressed during the course of pregnancy; on average, Scr changed from 177 ± 109 μmol/l in the early phase of pregnancy to 194 ± 149 μmol/l (p < 0.001) in the third trimester, and mean blood pressure increased from 97 ± 11 to 120 ± 19 mm Hg (p < 0.001). There were 37 cases with preeclampsia (49%). Fourteen cases showed a decrease in glomerular filtration rate (GFR) in the third trimester; 4 of these patients suffered a severe decrease in GFR (over 25%). The rate of obstetrical complications was high among preg nancies with renal impairment. Conclusion: Renal insufficiency associated with pregnancy is not rare, and renal function may deteriorate during the course of pregnancy.