Group B Streptococcus (GBS) Infection and in Preterm Labor Women Conceived Through IVF

\* Inclusion Criteria: To be eligible for enrolment into this trial, subject must fulfil all of the following criteria, unless specified otherwise * Being conceived through IVF * Moderate uterine contractions (2 contractions per 10 minutes, duration \< 30 seconds) * 20 0/7 to 36 6/7 weeks of gestation * Intact membrane * Cervical dilation ≤ 3 cm * Willing to participate into the study * Exclusion Criteria: To be eligible for enrolment in this study each subject must not meet any of the following criteria: * Having had intercourse during 24 hours before * Being suspected of amniotic leakage * Rupture of membrane identified by direct observation through speculum examination of amniotic fluid flow from cervix * Vaginal bleeding * Being suspected of placenta abruption, placenta previa * Having been treated with antibiotics within 1 week before * Vaginal douche within 48 hours before * Having used vaginal medicines during 48 hours before * Having vaginal ultrasound shortly before * Urine culture positive with GBS