Fasting Versus Fed: Effect of Oral Intake Prior to the Glucose Tolerance Test in Pregnancy

Studies suggest that the timing interval between oral intake and the 1-hour gestational diabetes screen may have a significant impact on gestational diabetes screening glucose levels. The investigators plan to conduct a prospective randomized trial comparing a 6-hour fast versus liberal oral intake within 2 hours prior to the glucose tolerance test in pregnancy in order to evaluate the effect of the fasting versus the fed state on routine gestational diabetes screening results.

Gestational diabetes (GDM) complicates approximately 400,000 pregnancies in the United States annually and is associated with significant adverse pregnancy outcomes, including increasing the lifetime risk of type 2 diabetes. The American College of Obstetricians and Gynecologists (ACOG) recommends that all pregnant women undergo GDM screening between 24-28 weeks gestation utilizing a 1-hour oral glucose tolerance test that was designed to be administered without regard to the last meal or time of day. However, studies suggest that the timing of one's last meal prior to the 1-hour GDM screen may have a significant impact on GDM screening glucose levels. In addition, providers routinely alter the timing of the 1-hour GDM screen based on patients' self reported oral intake prior to the exam. The investigators plan to conduct a prospective randomized trial comparing a 6-hour fast versus liberal oral intake within 2 hours prior to the glucose tolerance test in pregnancy in order to evaluate the effect of the fasting versus the fed state on routine GDM screening results.

Number of Participants With a Positive Gestational Diabetes Mellitus (GDM) Screen (>= 140 mg/dL) on the 1 Hour 50-g Oral Glucose Tolerance Test (OGTT)

Number of positive GDM screen (>= 140 mg/dL) on the 1 hour 50-g oral glucose tolerance test conducted between 24-28 weeks gestation This outcome was assessed in pregnant participants.

GDM diagnosis based on 1-hour OGTT ≥ 180 mg/dL or 2 elevated values on the 3-hour OGTT using Carpenter and Coustan criteria. This outcome was assessed in pregnant participants Carpenter and Coustan Criteria is as follows (if 2 or more values are elevated, this is gestational diabetes): Fasting glucose < 95; One hour glucose < 180; Two hour glucose < 155; Three hour glucose < 140

Primary = first Cesarean section for participant. This outcome was assessed in pregnant participants.

Shoulder dystocia is a birth injury (also called birth trauma) that happens when one or both of a baby's shoulders get stuck inside the mother's pelvis during labor and birth. This outcome was assessed in pregnant participants.

A third degree tear is a tear or laceration through the perineal muscles and the anal sphincter. A fourth degree tear goes through the anal sphincter all the way to the anal canal or rectum. This outcome was assessed in pregnant participants.

Inclusion Criteria: Pregnant patients 18 years and older Singleton gestation Pregnancy managed at Lucile Packard Children's Hospital (LPCH) Stanford outpatient obstetrics clinic Planned delivery at Lucile Packard Children's Hospital (LPCH) Stanford Labor and Delivery unit Exclusion Criteria: Pregestational diabetes Gestational diabetes diagnosed in the 1st trimester Less than 18 years of age Planned delivery outside LPCH Diabetes medication use prior to pregnancy Inability to give informed consent Chronic steroid use in pregnancy Less than 24 weeks of gestation at the time of the 1 hour oral glucose tolerance test Prior history of bariatric surgery Multifetal gestation