Bacteriuria in pregnancy
Research type
Research Study
Full title
Bacteriuria in pregnancy – an observational cohort study of asymptomatic bacteriuria and mixed urinary culture in relation to clinical outcomes
IRAS ID
288731
Contact name
Jane L D Currie
Contact email
Sponsor organisation
University College London
Clinicaltrials.gov Identifier
Z6364106/2021/03/213, Data protection registration number
Duration of Study in the UK
0 years, 9 months, 2 days
Research summary
One of the commonest reasons for antibiotics in pregnancy is asymptomatic bacteriuria (ASB). ASB means bacteria in the urine when it is cultured (grown in a laboratory) but without symptoms of a urine infection. Pregnant women in the UK are tested for ASB at their first midwife appointment.
ASB occurs in between 2% (one in fifty) to 10% (one in ten) pregnancies. Guidelines state that untreated, 30% (three in ten) women with ASB would get pyelonephritis (kidney infection), with increased risk of premature birth (birth before 37 weeks). Premature birth is the largest cause of illness and death in newborn babies.
However, this data arose from old, low quality studies. A recent large study in a country without routine ASB screening, found much lower rates of pyelonephritis and premature birth, and minimal benefit from antibiotics. That study used different methods, so results are not generalisable to UK. We do not know if screening for ASB is beneficial, despite being in national guidelines.
Is it a problem to give antibiotics for all ASB? Antibiotics are generally safe, but pregnancy medications should have benefits outweighing risks. Some bacteria in urine show antimicrobial resistance. One in ten (10%) cultures of the commonest urine bacteria show resistance to the commonest antibiotic used in pregnancy.
Why might there be a problem with the urine culture test? Recent studies have challenged it. For example, it was assumed that urine is sterile (no bacteria) when there is no infection; we now know healthy people have bacteria in their urine.
Another problem is that sometimes the culture result is 'mixed growth' (mixed bacteria). Pilot studies have suggested a link between mixed growth and premature birth. We do not know how to manage mixed growth. This has been identified as a national research priority.
REC name
North West - Preston Research Ethics Committee
REC reference
21/NW/0220
Date of REC Opinion
31 Jul 2021
REC opinion
Favourable Opinion