A Comparison Between Two Oral Hypoglycemics - Metformin and Glybenclamide for the Treatment of Gestational Diabetes Mellitus

Rationale Gestational diabetes mellitus (GDM) complicates 5-7% of pregnancies. Major hazards include macrosomia, polyhydramnios, labor trauma and neonatal hypoglycemia. The ADA and ACOG recommend glucose control in order to reduce the incidence of hyperglycemia induced complications. Glucose control can be achieved using diet and life style changes. Insulin is initiated in women who fail to obtain glucose control with diet alone. During the past 11 years oral hypoglycemic drugs have been tested and proven to be efficacious and safe.

Objectives

1. To compare the efficacy and safety of glybenclamide vs. metformin in the treatment of women diagnosed with GDM
2. To evaluate the improvement in glycemic control after the addition of a second oral hypoglycemic drug after failure of the first

Hypothesis GDM is one of the major conditions contributing to obstetrical complications and prenatal morbidity. Improving glycemic control, by means of improving compliance and patient satisfaction, will decrease obstetrical complications, maternal and neonatal morbidity and have positive long term health implications.

Study design Prospective, randomized, open label

Study population Women between the ages 18-45, diagnosed with GDM will be recruited. GDM will be defined by a pathological OGTT (according to Carpenter and Coustan criteria) performed at or after 13 weeks of gestation.

Study period From recruitment until discharge of the newborn baby after delivery

Power analysis Assuming 80% glycemic control with glybenclamide vs 55% with metformin, 52 women will be needed in each group in order to detect 25% difference in glycemic control rate with α=0.05 and β=0.2.

Study protocol Women will be randomized at recruitment. Demographic and obstetrical data will be collected. Average glucose levels during the previous two weeks, estimated fetal weight and amniotic fluid index, and lab exams reflecting glycemic control will be noted. Women will provide daily glucose levels via fax or mail once a week. Glycemic control will be evaluated by a daily chart, including 7 measurements: 3 preprandial, 3 postprandial and a 7th measurement at 10 pm. Women will be invited to a monthly follow-up, which will include a sonographic evaluation of fetal weight and amniotic fluid, and lab exams. Follow-up protocol after 38 w of gestation will be according to our ward's protocol. The study was approved by the local Helsinki committee.

Time table Duration: two years