Objective To present and to evaluate the conservative and surgical management of hydronephrosis in pregnancy.

Design Retrospective analysis of an interventional cohort.

Setting A tertiary maternity ward.

Sample Of the 30,552 women delivering in our institution between January 1998 and June 2001, 56 women (0.2%) were admitted to the prenatal care unit due to symptomatic hydronephrosis.

Methods For each patient, renal sonography, urinalysis, serum creatinine levels, white blood cell counts and urine culture were obtained. All patients were treated conservatively by analgesics, intravenous fluids and antibiotics. Failure of these measures: non-resolving infection, deteriorating renal function, absence of Doppler sonographic evidence of ureteral flow or intractable pain led to instrumental drainage of the affected kidney. A double pigtail polyurethane ureteric stent was passed under cystoscopic vision and sonographic guidance.

Main outcome measures Resolution of clinical symptoms.

Results Conservative treatment led to resolution in 52 women (92.9%), whereas four women (7.1%) failed to respond and were treated successfully and without complications by pigtail insertion. Early induction of labour was unnecessary and good perinatal outcome was the rule.

Conclusions Although the vast majority of cases of symptomatic hydronephrosis in pregnancy may be treated conservatively, pigtail insertion is an efficient and safe modality for the rare patient with refractory symptoms.