Clinical characteristics of the study population according to
the study period
During the study period, a total of 1,460 women were eligible for this
study. Table 1 summarizes the comparison of maternal ESBL-E vaginal
colonization according to the study period. The overall maternal ESBL-E
vaginal colonization rate was significantly higher in period 2 than in
period 1 (6.2% vs 2.4%, P < 0.001). Notably, the
positivity rate for E. coli colonization (14.3% vs 6.3%,P < 0.001) and the rate of ESBL-E-positive E.
coli colonization were significantly higher in period 2 than in period
1 (5.3% vs 1.7%, P < 0.001). However, there was no
significant difference in the rates of K. pneumoniae colonization
and ESBL-E-positive K. pneumoniae colonization between periods 1
and 2.
Table 2 compares the maternal baseline characteristics according to the
study period. The maternal age, primiparity, pre-pregnancy body mass
index, IVF-embryo transfer pregnancy rate, and short CL rate were
significantly higher in period 2 than in period 1. In particular, the
prior antibiotic treatment rate within 4 weeks was significantly higher
in period 2 than in period 1 (18.5% vs 13.9%, P = 0.018). We
additionally checked the indications for antibiotic use among the women
with prior antibiotic treatment (n = 238). Suspected diagnosis or
confirmed diagnosis of pPROM (n = 160) was most often indicated,
followed by PTL, prophylactic antibiotic use before or after cerclage,
IIOC, and fever, as shown in Table 2. No significant difference was
observed for any indication between the two periods.