The WAIT Trial: Waiting Versus Active Induction at Term in Women With A1 Gestational Diabetes Mellitus

This multicenter, open-label, superiority randomized controlled trial will evaluate whether delaying planned induction from 40 weeks to 41 weeks improves delivery outcomes in women with A1 gestational diabetes mellitus (A1 GDM). The study is designed to enroll 1,500 eligible women (750 per group), all of whom are planned for vaginal delivery. Eligible participants are women aged 18-40 years with singleton pregnancy and who are primiparous. GDM will be diagnosed using OGTT at 24-28 weeks, and participants must meet criteria for A1 GDM, meaning blood glucose is controlled with diet and exercise only (no insulin or other glucose-lowering medications during pregnancy). After providing written informed consent, participants will be randomized 1:1 to one of two pre-specified induction strategies. Control group (planned induction at 40 weeks): Participants will have planned induction at 40+0 weeks (time window 39+6 to 40+0). If spontaneous labor occurs before or during the window, obstetric management will follow routine clinical practice. If labor has not started by the end of the window, induction will be performed according to the protocol. Intervention group (expectant management until 41 weeks): Participants will be managed expectantly until 41+0 weeks with planned induction in the 41+0 to 41+1 weeks window. If spontaneous labor occurs before or during the window, routine obstetric management will be used. If labor has not started by the end of the window, induction will be performed according to the protocol. Participants will be followed from randomization until delivery and hospital discharge, with selected outcomes followed up to postpartum day 42. The primary outcome is the cesarean delivery rate. Secondary outcomes include maternal outcomes such as postpartum hemorrhage and other obstetric complications, neonatal/perinatal outcomes including perinatal death, and need for respiratory support, as well as selected health-economic and patient-reported outcomes. All participating centers will apply standardized procedures for screening, monitoring, induction methods, and data collection. An independent Data and Safety Monitoring Board (DSMB) and a blinded Clinical Endpoint Committee will monitor safety and validate the primary outcome. The trial is expected to be completed within approximately 18 months after initiation of recruitment, and the results will provide high-quality evidence to inform timing of delivery for women with A1 GDM in China.

Inclusion Criteria: * Aged 18-40 years; * Singleton pregnancy; * Nulliparous; * Diagnosed with gestational diabetes mellitus (GDM) by oral glucose tolerance test (OGTT) at 24-28 weeks of gestation; * At screening/enrollment, classified as A1 GDM, defined as good glycemic control after exercise counseling and nutritional management. Both of the following criteria must be met: (1) No use of insulin or other glucose-lowering medications during pregnancy up to screening/enrollment, verified through medication orders in the hospital information system (HIS); and (2) The clinician assesses overall glycemic control during pregnancy as meeting target and explicitly documents A1 GDM in the outpatient medical record. * Provides written informed consent. Exclusion Criteria: * Maternal factors: signs of labor; prelabor rupture of membranes; history of cesarean delivery or uterine surgery (e.g., myomectomy); clinically assessed pelvic contraction (e.g., pelvic outlet diameter ≤7.5 cm); cervical cerclage during the current pregnancy; planned cesarean delivery or any known contraindication to vaginal delivery; or severe pregnancy-related complications or comorbidities considered by the investigator to preclude tolerance of vaginal delivery, such as severe heart disease complicating pregnancy, intrahepatic cholestasis of pregnancy, hypertensive disorders of pregnancy, psychiatric disorders/cognitive impairment, autoimmune diseases, or severe anemia. * Fetal factors: non-cephalic presentation; intrauterine fetal demise; fetal distress; fetal structural malformations or chromosomal abnormalities; fetal growth restriction (ultrasound-estimated fetal weight below the 10th percentile); or large-for-gestational-age fetus (ultrasound-estimated fetal weight above the 90th percentile). * Amniotic fluid factors: oligohydramnios, defined as an amniotic fluid index (AFI) ≤5 cm or a maximum vertical pocket (MVP) ≤2 cm; or polyhydramnios, defined as an AFI ≥25 cm or an MVP ≥8 cm. * Placental factors: placenta previa, placenta accreta spectrum, vasa previa, or similar conditions. * Medication-related contraindications: contraindications to induction agents such as misoprostol or oxytocin, including asthma, glaucoma, a scarred uterus, or drug allergy/hypersensitivity.