Pyelonephritis affects 1–2% of pregnant women, and is associated with significant maternal and fetal morbidity. Antenatal pyelonephritis has been associated with PPROM (preterm premature rupture of membranes), preterm labour, low birth weight (LBW) and prematurity. A three-year retrospective dual-centre cohort study of antenatal pyelonephritis cases was conducted in two neighbouring Irish maternity hospitals – the Rotunda Hospital (RH) and the National Maternity Hospital (NMH). Patient demographics, clinical presentation, investigations, management and maternal/neonatal outcomes were recorded. A total of 47,676 deliveries (24,768 RH; 22,908 NMH) were assessed. 158 cases of antenatal pyelonephritis were identified (n= 88 RH,n= 70 NMH), with an incidence of 0.33%. The median age was 28 years. The median gestation was 27 + 6 weeks, with 51% presenting before 28 weeks’ gestation. Risk factors included; obesity (18.4%), diabetes mellitus (13.3%) and self-reported clinical history of recurrent urinary tract infection (28.5%). Rate of relapse with UTI in the same pregnancy was 8.2%. Renal ultrasound was performed in 30.4%. Predominant uropathogens wereEscherichia coli(60%),Klebsiella pneumoniae(11%) andProteus mirabilis(5%). 7.5% of cases had a concurrent bloodstream infection, 13.3% of cases were complicated by sepsis and 1.9% with septic shock. Complications including PPROM (6.3%), preterm delivery < 37 weeks’ gestation (11%), LBW < 2,500 g (8.2%) were comparable between sites. Delivery within 72 hours of diagnosis was noted in 7% (n= 11) of patients, of which three were preterm and one had LBW. Appropriate and prompt investigation and management of antenatal pyelonephritis is essential given the associated maternal and neonatal morbidity.