DECIDE: A Comparative Effectiveness Trial of Oral Metformin versus Injectable Insulin for the Treatment of Gestational Diabetes

Diabetes during pregnancy, also known as gestational diabetes (GDM), is common and increases the chance that the mother and infant can experience complications, such as cesarean delivery and neonatal intensive care unit admission. The number of pregnant people who are developing GDM is increasing every year in the United States and is more common in pregnant people who are from minority communities as well as those who are living with obesity. Treatment decreases the risk of complications for the mother and child. The first step is improving diet and increasing exercise to control blood sugar. Even with improved diet and exercise, more than one out of every four pregnant people with GDM needs medication to control their blood sugar. 

Because GDM is common and can lead to life-long complications for the mother and infant, it is important to treat it. Pregnant people with GDM and their healthcare providers lack the necessary information required to make decisions on which medication to use. The most common medication is insulin, which requires taking daily injections and can be inconvenient and costly. Another option is metformin, which is an oral pill that also controls blood sugar and is cheaper and more convenient to take. Some professional societies say insulin is the best option, but others say metformin is a reasonable choice. It is not clear whether metformin works as well as insulin in preventing pregnancy complications due to high blood sugar, and whether metformin is as safe as insulin for children whose mothers took it during pregnancy. It is also important to understand whether there are factors that make some patients more or less likely to prefer metformin compared to insulin. 

In the United States, there have been no clinical trials testing how well metformin works compared with insulin to prevent pregnancy complications in pregnant people with GDM. The overall goals of this large study of pregnant people with GDM who require medication are to figure out:  

1. Whether metformin works as well as insulin to prevent pregnancy complications. 
2. Whether metformin is equally as safe as insulin for children who were born to mothers who received treatment. 
3. Whether there are reasons why pregnant people with GDM prefer metformin versus insulin. 

The study will randomly assign 1,572 diverse pregnant people with GDM to either oral metformin pills or insulin injections. Mothers and their children will be followed from the beginning of their treatment until two years after delivery. The study team will:  

1. Compare how often people taking metformin versus insulin have complications of pregnancy (such as a baby that is too big, has low blood sugar or needs to go to a special care unit after delivery) and rate their overall health and experience being pregnant and having a baby. 
2. Compare how often children at 2 years of age who were born to mothers who took metformin versus insulin weigh more than a healthy amount. 
3. Determine whether there are things that make it easier to take metformin or insulin to treat gestational diabetes. 

The research team will also work with individuals who pay for, support and receive medical care in pregnancy to make sure patients and the medical community are aware of and can use the study findings. 

This study will show whether metformin works as well as insulin for pregnant people with GDM. It will also answer an important question that could improve the life-long health of mothers with GDM and their children and may decrease differences in health outcomes among different groups of pregnant people. When completed, this will be the largest study producing up-to-date information on the best way to treat GDM and prevent complications in and after pregnancy. Because both metformin and insulin are commonly used to treat diabetes in pregnancy, the study team believes that the findings from this research will quickly be utilized to guide care for patients. The diverse research team is well-equipped to design, run and complete this study. What is learned from this research not only has the potential to improve the quality of life for pregnant people with GDM and their children but also to improve overall patient care.