Aim: To assess the possible protective effect of exclusive breastfeeding against first-time febrile urinary tract infection (UTI) in children. Methods: Two children's hospitals and local child health centres in the Gteborg area, Sweden, participated in a prospective case-control study. In total, 200 consecutive cases (89M, 111F), aged 0-6 y, presenting with first-time febrile UTI were enrolled. The mean ± SD age was 0.98 ± 1.15 y. As control subjects, 336 children (147M, 189F) were recruited from the child health centre of the case, matched for age and gender and included consecutively for each case during the first days after diagnosis. The duration of exclusive breastfeeding was obtained from the case and controls by a standardized procedure. Results: Ongoing exclusive breastfeeding gave a significantly lower risk of infection. A longer duration of breastfeeding gave a lower risk of infection after weaning, indicating a long-term mechanism. The protective role of breastfeeding was strongest directly after birth, then decreased until 7 mo of age, after which age no effect was demonstrated.

Conclusion: A protective role of breastfeeding against UTI was demonstrated. The study provides statistical support to the view that breast milk is a part of the natural defence against UTI.