The Exploration of Prolonged Treatment With Vaginal Progesterone to Prevent Preterm Birth From IVF Fresh Embryo Transplantation Cycle: a Randomized Controlled Trial

Inclusion criteria were: age 20-40 years; indication for assisted reproductive technology (ART) with fresh embryo transfer via in vitro fertilization (IVF); singleton pregnancy; and willingness to participate and provide written informed consent. Exclusion criteria were: age >40 years; history of second-trimester miscarriage or cervical insufficiency; ovarian dysfunction or prior ovarian surgery; uterine malformation; conditions associated with abnormal uterine cavity morphology; abnormal cervical morphology or function, or history of cervical surgery; refractory vaginitis; multiple pregnancy; severe medical or surgical comorbidities; participation in another clinical trial within 90 days before randomization, or use of an investigational drug within 30 days; inability or poor compliance for long-term follow-up; and any other condition that, in the investigator's judgment, could interfere with trial implementation or outcome evaluation.

Control group: The administration of vaginal progesterone (90mg/d) began from positive HCG in blood/urine until 12 weeks of gestation. Regular delivery examinations were conducted, and cervical length was detected by B-ultrasound at 12, 16, 20 and 24 weeks of gestation respectively, while fetal growth and development were monitored. Follow-up was continued until the end of delivery.

Trial group: The administration of vaginal progesterone (90mg/d) began from positive HCG in blood/urine until 24 weeks of gestation. Regular delivery examinations were conducted, and cervical length was detected by B-ultrasound at 12, 16, 20 and 24 weeks of gestation respectively, while fetal growth and development were monitored. Follow-up was continued until the end of delivery.

Observation index: The gestational age of delivery, symptoms of preterm birth and gestational age, gestational age at preterm birth or abortion, fetal growth and development, neonatal outcomes, and drug-related adverse reactions were recorded for each participant.