| 1% CHG (n=341) | 2% CHG (n=344) | Risk difference (95% CI) | P value | P value for test of interaction* |

Percentage of negative post-cleansing skin swabs, n (%) | 317 (93.0) | 329 (95.6) | −2.7% (−6.2% to +0.8%) | 0.13 | |

Gestation age, n/N (%) | |||||

26^{0/7}−27^{6/7}weeks | 9/10 (90.0) | 8/10 (80.0) | −10% (−40% to +20%) | 0.53 | 0.35 |

28^{0/7}−34^{6/7} weeks | 178/189 (94.2) | 189/191 (98.9) | −4.8% (−8.4% to −1.1%) | 0.01 | |

35^{0/7}−42^{6/7} weeks | 130/142 (91.5) | 132/143 (92.3) | −0.7% (−7% to +5.5%) | 0.81 | |

Contact dermatitis severity scoring, n (%)† | |||||

0 hours | 8 (2.3) | 8 (2.3) | +0.02% (−2.2% to +2.2%) | 0.98 | |

6 hours | 0 | 0 | – | ||

12 hours | 0 | 0 | – | ||

24 hours | 0 | 0 | – | ||

Plasma chlorhexidine concentration at 24–48 hours in ng/mL, median (IQR) | 19.6 (12.5–36.4) (n=24) | 12.6 (8.7–26.6) (n=17) | – | 0.24 |

*Tests the null hypothesis that the treatment group effect on the outcome is the same for each gestational age at birth strata.

†Since the maximum score observed was a score of 1 at 0 hours, and no skin-related adverse effects were observed at 6, 12 and 24 hours post-application, we present the data as proportion of instances when a score of 1 was observed in the two groups.