Methods	RCT.
Participants	Pregnant women seeking antenatal care visits at the participating centers betweenMarch 2004 and March 2007 and capable of giving informed consent were recruited at gestational ages between 12 weeks and 32 weeks. 778 patients were recruited successfully for the study Inclusion criteria: asymptomatic bacteriuria (> 100,000 cfu/ml); microorganism sensitive to nitrofurantoin; absence of symptoms suggesting UTI. Exclusion criteria: history of treatment for UTI during the current pregnancy; presence of an underlying disease that required continuous steroids and/or antibiotic.
Interventions	Group 1: 386 women were allocated to receive nitrofurantoin 100 mg twice a day on the first day plus placebo twice a day to complete 7 days Group 2: 392 women were allocated to receive nitrofurantoin 100 mg twice a day for 7 days
Outcomes	Primary outcomes: Symptomatic infection: at 2 weeks: group 1: 5/371 (1.3%); group 2: 7/370 (1.9%); in the following weeks before delivery: group 1: 10/354 (2.8%); group 2: 12/349 (3.4%). Persistent infection: at 2 weeks: group 1: 90/371 (24.3%); group 2: 51/370 (13.8%). Recurrent infection: not reported. Shift to another antibiotic: not reported. Adverse effects: Nausea: group 1: 23/375 (6.1%); group 2: 33/385 (8.6%). Headache: group 1: 17/375 (4.5%); group 2: 22/385 (5.7%). Flatulence: group 1: 15/375 (4.0%); group 2: 9/385 (2.3%). Others: group 1: 20/375 (5.3%); group 2: 26/385 (6.8%) Secondary outcomes: Preterm delivery: group 1: 39/353 (11%); group 2: 31/349 (8.9%) Preterm labor: not reported. Neonatal infection: not reported. RDS in the neonate: not reported. Admission to NICU: not reported. Duration of neonatal respiratory support: not reported Other outcomes: Low birthweight: group 1: 48/364 (13.2%); group 2: 28/350 (8%). Congenital malformations group 1: 5/364 (1.4%); 4/350 (1.1%). Mean birthweight: group 1: 3.059 g; group 2: 3.159 g. Mean birth gestational age: group 1: 38.4 weeks; group 2: 38.7 weeks
Notes
Risk of bias
Item	Authors’ judgement	Description
Adequate sequence generation?	Yes	Randomization codes were independently generated for each study site by the statistical unit at the Department of Reproductive Health and Research, the World Health Organization, Geneva, Switzerland. The random allocation sequence was generated using computer-generated random numbers with randomly varying blocks of 6/8 (SAS software, SAS Institute, Inc., Cary, NC)
Allocation concealment?	Yes	The random allocation was concealed by using sealed, opaque treatment boxes numbered sequentially using the sequence described above
Blinding? Participant	Yes	Yes, placebo was used.
Blinding? Clinician	Yes	Yes, placebo was used.
Blinding? Outcome assessor	Yes	Yes, placebo was used.
Incomplete outcome data addressed? All outcomes	Yes	Low attrition. Sensitivity analysis was done where it was appropriate
Free of selective reporting?	Yes	All outcomes were presented.
Free of other bias?	Yes