The Best Timing of Delivery in Women With GDM Study

Inclusion Criteria: * singleton pregnant women * in vertex presentation * GDM that is controlled with only diet and exercise * at 37 weeks 0 days to 37 weeks 6 days of gestation * more than 18 years old * have no other contraindications to vaginal delivery. Exclusion Criteria: * prior caesarean section or myomectomy * any known contraindications to vaginal delivery * uncertain gestational age * non reassuring foetal wellbeing necessitating delivery * maternal pregnancy-related disease necessitating delivery (any hypertensive disorder, cardiac disease, renal insufficiency、immune diseases, et al.) * placenta previa, accreta, vasa previa * known foetal anomaly * negative reproductive history * ruptured membranes or known oligohydramnios (defined as AFI \< 5 or MVP \< 2 ) before 37weeks 6 days of gestation * fetal growth restriction, defined as EFW \< 10th percentile * known HIV positivity because of modified delivery plan * signs of labor (regular painful contractions with cervical change) before 37weeks 6 days of gestation.