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To screen or not to screen for asymptomatic bacteriuria in pregnancy: A comparative three-year retrospective review
Elaine Houlihan1, Rachel Barry2, Susan J Knowles3
1Dr Elaine Houlihan and Dr Rachel Barry are joint first authors and contributed equally to this work; Department of Microbiology, National Maternity Hospital, Dublin, Ireland.
Insights
Screening for asymptomatic bacteriuria (AB) in pregnant individuals is not associated with increased rates of pyelonephritis or preterm birth. Omitting routine AB screening may be a cost-effective strategy without compromising care quality.
Area of Science:
- Obstetrics and Gynecology
- Infectious Diseases
- Public Health
Background:
- Current Irish national guidance recommends screening for asymptomatic bacteriuria (AB) during pregnancy (12-16 weeks gestation) and treating with antimicrobials.
- This recommendation is based on limited evidence suggesting a link between AB and adverse pregnancy outcomes like preterm birth and low birth weight infants (LBWI).
Purpose of the Study:
- To compare rates of antenatal pyelonephritis, preterm birth, and LBWI between maternity hospitals with and without routine asymptomatic bacteriuria screening.
- To evaluate the impact of omitting AB screening on key obstetric outcomes.
Main Methods:
- A retrospective review of deliveries over three years (2018-2020) was conducted in two Irish maternity hospitals.
- One hospital (Rotunda Hospital - RH) screened for AB, while the other (National Maternity Hospital - NMH) did not.
- Patients admitted for pyelonephritis requiring intravenous antibiotics were identified, and outcomes were compared between screened and unscreened populations and across hospitals.
Main Results:
- No statistically significant difference was found in antenatal pyelonephritis rates (p=0.34) or preterm births (p=0.21) between the two hospitals.
- The hospital with screening (RH) had a significantly higher rate of LBWI (6.45%) compared to the non-screening hospital (NMH) (5.68%) (p<0.004).
- Subgroup analysis within the screening hospital showed no significant difference in pyelonephritis rates between screened and unscreened patients, or compared to the non-screening hospital.
Conclusions:
- Omission of routine asymptomatic bacteriuria screening did not lead to increased rates of antenatal pyelonephritis, preterm birth, or LBWI.
- These findings suggest that selective screening for AB in high-risk pregnancies could be a more cost-effective approach while maintaining quality of care.
- The study may inform future national guidelines on antenatal screening protocols for asymptomatic bacteriuria.
Background:
Current national guidance in Ireland states that asymptomatic bacteriuria (AB) should be screened for at 12-16 weeks' gestation and treated with a seven-day course of antimicrobials, due to the potential risk of preterm birth and low birth weight infants (LBWI), however, this is based on low quality evidence.
Methods:
Over a three-year period (2018-2020), a retrospective review was undertaken in two neighbouring maternity hospitals; one of which screens for AB (Rotunda hospital (RH)) and one which does not (National Maternity Hospital (NMH)). Patients were included on the basis of fulfilling the IDSA definition for pyelonephritis and requiring admission for intravenous antibiotics. Rates of antenatal pyelonephritis were compared between hospitals, and between screened and unscreened populations. Secondary outcomes including rates of preterm births and LBWI were compared across sites.
Results:
A total of 47,676 deliveries between the two centres (24,768 RH; 22,908 NMH) were assessed, of which 158 patients met inclusion criteria for antenatal pyelonephritis (n = 88 RH, n = 70 NMH). There was no statistically significant difference in the rate of antenatal pyelonephritis (p = 0.34) or preterm births (p = 0.21) across sites. RH had a significantly higher rate of LBWI at 6.45% versus 5.68% of all births in NMH (p=<0.004). Given the screening rate in RH was below 100%, this cohort was further subdivided into 'RH screened' and 'RH unscreened'. There was no statistically significant difference in the rate of antenatal pyelonephritis both between the 'NMH unscreened' group (n = 70) versus the 'RH screened' group (n = 62) (p = 0.53), or in the 'RH screened' group (n = 62) versus the 'RH unscreened' group (n = 26) (p = 0.53).
Conclusion:
Omission of a screening programme for AB in NMH did not result in higher rates of antenatal pyelonephritis, preterm birth or LBWI. Our findings may inform decision-making on screening protocols and whether selective screening (i.e. screening in high-risk patients only) could be more cost-effective without compromising best quality of care.
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