To determine the accuracy of antenatal renal pelvis measurement as a screening tool for renal anomalies we reviewed the antenatal ultrasounds performed at our institution over 1 year. Renal pelvis dilation was found in 3.8% of pregnancies followed by our obstetrics department. In nine (17.6%) infants renal anomalies were detected after birth, the remaining cases remained unchanged or resolved over a 1-year postnatal follow-up. In our series dilations of less than 10 mm in utero resolved in the first months after birth while dilations greater than 15 mm were all associated with malformations of the genitourinary tract. The choice of the most appropriate follow-up for dilations between 10 and 15 mm remains an issue because these dilations can herald renal anomalies.