Threshold for Initiation of Medical Treatment for Women With Gestational Diabetes

Gestational diabetes mellitus (GDM) affects 5-8% of pregnant women, many of whom will require
treatment beyond diet and exercise. Despite this high prevalence, there is no consensus
regarding the glycemic threshold for conversion from diet to medical treatment for GDM. No
randomized studies have been performed on how to define failure with diet and exercise and
currently, the need to start insulin or oral hypoglycemic agents is at the provider's
discretion. It is important to establish criterion of pharmacotherapy initiation for GDM in
pregnancy as GDM under-treatment leads to increased rates of adverse obstetric outcomes
associated with poor glycemic control including macrosomia, pre-eclampsia, cesarean delivery,
shoulder dystocia, birth trauma, neonatal hypoglycemia and hyperbilirubinemia, childhood
obesity and metabolic syndrome in the offspring. In contrast, overtreatment for women comes
at increased cost due to overutilization of resources, increased expense, and adverse effects
of the medications themselves.

The goal of this study is to compare two different thresholds for initiation of medical
treatment for GDM. Pregnant women diagnosed with GDM (N=284) will be randomized to either
start pharmacotherapy when they have reached at least 20% or at least 40% of capillary blood
glucose (CBG) values above the target goal. The investigators hypothesize that a lower
threshold of 20% elevated CBG levels, compared to 40%, will lead to lower rates of obstetric
and medical complications.

Aim 1: To compare the rate of a composite outcome between two thresholds for medical
treatment initiation for GDM. Women who receive the diagnosis of GDM and meet eligibility
criteria will be randomized to start insulin or an oral hypoglycemic agent when the number of
CBG values above target reaches 20% or 40%. The primary outcome will be a composite of
neonatal macrosomia, shoulder dystocia, neonatal hypoglycemia, neonatal hyperbilirubinemia,
preterm delivery, neonatal intensive care unit (NICU) admission, and stillbirth or neonatal
death. The investigators hypothesize that women who receive treatment with stricter limits of
abnormal blood glucose levels will have lower rates of these poor outcomes.

Aim 2: To compare the rates of cesarean delivery between two thresholds for medical treatment
initiation for GDM. The investigators hypothesize that women who receive treatment with
stricter limits of abnormal blood glucose levels will have lower rates of cesarean delivery.

Inclusion Criteria:

- Viable singleton pregnancy

- Age >= 18 years old

- Diagnosed with gestational diabetes mellitus

Exclusion Criteria:

- Pre-gestational diabetes

- Significantly abnormal blood glucose testing, suggestive of the presence of
pre-gestational diabetes

- Women who check blood sugars on average less than 2 times per day after appropriate
counseling