Study population
This retrospective cohort study included consecutive pregnant women who
were admitted to the high-risk pregnancy unit of our institution between
14+0/7 and 35+6/7 weeks of gestation
and delivered a baby at our hospital. The indications for admission were
preterm premature rupture of membrane (pPROM), preterm labor (PTL),
incompetent internal os of the cervix (IIOC), and short cervical length
(CL) (defined as a CL of <25 mm on transvaginal ultrasound).
The study period was from January 2010 to December 2020 and was
arbitrarily divided into period 1 (January 2010 to July 2015) and period
2 (August 2015 to December 2020) to evaluate changes in the association
of ESBL-E vaginal colonization over the time periods. The study was
approved by our institutional review board (no. 2020-08-006). The
requirement for written informed consent was waived owing to the
retrospective design of our study. Prior to analysis, all patient
records were anonymized.