Comparison of Two Screening Strategies for Gestational Diabetes (GDM2)

Impaired glucose metabolism (gestational diabetes (GDM) and mild hyperglycemia) that occurs
during pregnancy is associated with an increased risk for pregnancy complications and is also
an early indication of long-term metabolic dysfunction leading to diabetes and cardiovascular
disease. In the US, GDM is diagnosed using a two-step screening and diagnostic approach. The
International Association of Diabetes and Pregnancy Study Group (IADPSG) proposed a one-step
diagnostic approach that broadens the definition of GDM by lowering the cutoff values to
include women with milder forms of hyperglycemia, who would have screened normal under the
current two-step approach. The goal of these recommendations is better identification of
women at risk for pregnancy complications and long-term metabolic dysfunction, but it results
in a significant increase in the prevalence of GDM. The NIH GDM Consensus Development
Conference committee does not recommend changing from the current two-step
screening/diagnostic approach to the IADPSG one-step diagnostic approach without trials
demonstrating that increasing the number of women diagnosed as having GDM results in better
outcomes. We aim to 1) conduct a "real world" randomized controlled trial (RCT) to determine
differences in short-term perinatal health outcomes between the two predominant GDM screening
approaches, and 2) prospectively follow the mothers to examine their metabolic risk profiles
and the growth of their infants at 1 year postpartum. Based on a pilot study, we propose a
single site blinded RCT of 920 pregnant women ages 18-45 years without a diagnosis of
diabetes, with a singleton pregnancy (18-24 wks gestation). Participants will have a
non-fasting 1 hour 50 gm glucose challenge test (GCT) performed between 24-28 weeks'
gestation. Women with 50 gm GCT results < 200 mg/dL will be randomized to receive either a
fasting 2 hour 75 gm oral glucose tolerance test (OGTT) or a 3 hour 100 gm OGTT. GDM will be
diagnosed using the IADPSG criteria for women receiving the 75 gm OGTT and Carpenter-Coustan
criteria for women receiving the 100 gm. Participants and their physicians will be informed
of the diagnosis of GDM, but blinded to the specific test results and diagnostic criteria.
Participants with GDM will receive treatment from their primary provider. Questionnaires will
be used to assess participants' and physicians' views on GDM testing. Metabolic profiles will
be assessed at randomization and at a year postpartum. The primary outcome measure is
large-for-gestational age fetal growth. The rationale for this RCT is that this is a unique
opportunity to compare the two methods. At the end of the study, we will know whether women
diagnosed at lower glucose levels with the IADPSG criteria are more likely to have adverse
perinatal outcomes. We hypothesize that using IADPSG diagnostic criteria will result in
greater detection of women with impaired glucose metabolism and treating these women will
reduce adverse perinatal outcomes and prevent long-term metabolic dysfunction. This study
will provide level A data for endorsing universal screening guidelines for GDM by major
organizations and implementation into clinical care.

Inclusion Criteria:

- Pregnancy between 18-24 weeks of gestation

- Singleton gestation

- Planning to deliver at Magee-Womens Hospital, Pittsburgh, PA

Exclusion Criteria:

- Preexisting type 1 or 2 diabetes

- Diabetes diagnosed at less than 24 weeks gestational age (GA)

- Multiple gestations ( e.g. twins or triplets)

- Hypertension requiring medications

- Corticosteroid (IM, oral or IV) use in the 30 days prior to enrollment

- Major congenital anomaly with anticipated preterm delivery due to maternal or fetal
indications < 28 wks GA

- Inability to complete the glucose testing before 30 completed weeks GA

- Advanced HIV( on medications that cause hyperglycemia), severe liver disease, gastric
bypass surgery or other illness/surgeries that preclude them from drinking the glucola
solution.