Clinical characteristics of the study population
We collected data on maternal characteristics, including age, parity,
pre-pregnancy body mass index, history of preterm birth (PTB),
plurality, infertility treatment (intrauterine insemination and in
vitro fertilization [IVF]) of index pregnancy, gestational age at
admission, diagnosis at admission (pPROM, IIOC, PTL, or short CL), and
use of antibiotics before admission. Prior antibiotic treatment was
defined as the use of antibiotics within 4 weeks prior to the vaginal
culture test. Perinatal outcomes included gestational age at delivery,
mode of delivery, abortion, stillbirth, histologic chorioamnionitis,
sex, birth weight, Apgar score, neonatal mortality, neonatal intensive
care unit admission rate, and neonatal sepsis. Abortion included all
fetal loss in utero occurring before 20 weeks of gestation, while
stillbirth included fetal loss occurring beyond 20 weeks of gestation
with 5-min Apgar scores of 0. According to the protocol used by Redline
et al.,15 histologic chorioamnionitis was reviewed by
a single pathologist (JSK) as previously defined.16Early-onset neonatal sepsis (EONS) was defined as neonatal sepsis within
the first 3 days of life, including infection by any kind of organism.
Suspected sepsis was diagnosed clinically by pediatricians, while proven
sepsis was diagnosed when microorganisms were isolated from the blood or
cerebrospinal fluid of neonates.