Rethinking urinary tract infections in women with abdominal pain in pregnancy: a prospective case-control study

Abstract Background: Abdominal pain in pregnancy may be caused by urinary tract infection (UTI), which is associated with preterm birth and pyelonephritis. Standard urine culture is insensitive; alternative tests, previously studied in chronic UTI, may improve UTI diagnosis in pregnancy. We hypothesised that women with abdominal pain in pregnancy may have urinary pathology not detected by standard tests. Methods: This single-centre, prospective case-control observational study compared patients presenting with abdominal pain after 14 weeks’ gestation, using both standard and alternative tests, against gestation-matched patients presenting with another non-abdominal pain acute problem, and asymptomatic patients attending routine antenatal care. Urine samples were a clean-catch midstream void. Standard tests were urinary dipstick, microscopy and culture. Alternative tests were: (1) objective symptoms inventory; (2) quality of life assessment (EQ-5D-5L); (3) fresh unspun urine microscopy; (3) urinary ATP; (4) enhanced sediment culture; (5) urinary IL-6, IL-8 and lactoferrin; (6) urothelial cell analysis. Non-parametric statistical methods were used. Results: Pregnant women whether with abdominal pain (n = 50), other acute hospital presentations (n = 58) or attending routine antenatal care (n = 51), had symptoms of UTI with scores equivalent to those seen in patients with chronic UTI. Women presenting acutely with abdominal pain did have more pain symptoms, nocturia, and lower quality of life scores, with a different distribution of bacteria using enhanced urine culture, but they had equivalent rates of positive standard urine culture compared to those with no pain or those in routine antenatal care. Subsequently they were more likely to be diagnosed with a UTI and prescribed antibiotics. Urinary symptoms and markers of urinary pathology were prevalent in all groups, but different in those clinically diagnosed with UTI. Conclusions: Our study shows that current standard testing for UTI in pregnancy, and understanding of what is normal and abnormal, is inadequate. The use of alternative tests, well validated in a chronic UTI research programme, raises questions about current urine testing practice in pregnancy and the assumptions that drive them. Further research should examine these tests in different pregnancy contexts, to determine if they can enhance UTI diagnosis, better guide management of urine pathology in pregnancy and improve pregnancy outcomes.