BACKGROUND: Randomized trials from South Asia indicate umbilical cord chlorhexidine cleansing reduces mortality and omphalitis. No community-based data are available on bacteriological profile of the cord, early neonatal colonization dynamics, or impact of cord cleansing on colonizing organisms. Such data could clarify the design of scaled chlorhexidine interventions.METHODS: Umbilical swabs were collected at home (days 1, 3, 6) after birth from infants participating in a trial of 3 cord-care regimens (no chlorhexidine, single cleansing, multiple cleansing) in Sylhet, Bangladesh. Overall and organism-specific positivity rates were estimated by cord-care regimen and by day of collection.RESULTS: Between September 2008 and October 2009, 1923 infants contributed 5234 umbilical swabs. Positivity rate was high (4057 of 5234, 77.5%) and varied substantially across groups. Immediate (day 1) reductions in cord colonization were observed in single- (prevalence rate ratio = 0.75, 95% confidence interval: 0.70-0.81) and multiple- (prevalence rate ratio = 0.71, 95% confidence interval: 0.66-0.77) cleansing groups. Reductions persisted and increased in magnitude through day 6 only if babies received multiple applications. On days 1, 3, and 6, respectively, multiple cleansing consistently reduced invasive organisms such as Escherichia coli (49%, 64%, and 42% lower), Klebsiella pneumoniae (46%, 53%, and 33% lower), and Staphylococcus aureus (34%, 84%, and 85% lower).CONCLUSIONS: Cord cleansing with 4.0% chlorhexidine immediately after birth reduces overall and organism-specific colonization of the stump. Reductions are greater and sustained longer with daily cleansing through the first week of life, suggesting that programs promoting chlorhexidine cleansing should favor multiple over single applications.