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

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.

• Fasting before gestational diabetes screen (Behavioral): Fasting for at least 6 hours before 1-hour gestational diabetes screen.
• Per oral intake of food and drink (Behavioral): Per oral intake of food and drink within 2 hours of gestational diabetes screen

Primary outcomes

• 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) [Day of GDM screen (occurring between 24-28 weeks gestation)]: 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.

Secondary outcomes

• Mean Gestational Age at OGTT Screen [Day of GDM screen (occurring between 24-28 weeks gestation)]
• Mean Glucose Level at the OGTT Screen [Day of GDM screen (occurring between 24-28 weeks gestation)]
• Number of Participants With Positive GDM Diagnosis Based on the OGTT [Day of GDM screen (occurring between 24-28 weeks gestation)]: This outcome was assessed in pregnant participants.
• Average Time of Last Oral Intake Prior to the OGTT Screen [Day of GDM screen (occurring between 24-28 weeks gestation)]: Average number of hours since the participant's last oral intake prior to OGTT screen
• Number of Participants With Positive GDM Diagnosis [Day of OGTT (occurring at 24-28 weeks gestation up to 42 weeks gestation)]: 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
• Mean Gestational Age at Delivery [At time of delivery (Up to 42 weeks' gestation)]
• Number of Participants Who Delivered Vaginally [At time of delivery (up to 42 weeks' gestation)]: This outcome was assessed in pregnant participants.
• Number of Participants Who Delivered Via Operative Vaginal Birth [At time of delivery (up to 42 weeks' gestation)]: This outcome was assessed in pregnant participants.
• Number of Participants Who Delivered Vaginally After a Prior Cesarean Section [At time of delivery (up to 42 weeks' gestation)]: This outcome was assessed in pregnant participants.
• Number of Participants Who Delivered Via a Primary Cesarean Section [At time of delivery (up to 42 weeks' gestation)]: Primary = first Cesarean section for participant. This outcome was assessed in pregnant participants.
• Number of Participants Who Delivered Via a Repeat Cesarean Section [At time of delivery (up to 42 weeks' gestation)]: This outcome was assessed in pregnant participants.
• Number of Participants Complicated by Shoulder Dystocia at Delivery [At time of delivery (up to 42 weeks' gestation)]: 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.
• Number of Participants Complicated by Third or Fourth Degree Perineal Laceration [At time of delivery (up to 42 weeks' gestation)]: 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.
• Number of Participants With Post-partum Hemorrhage [Up to 6 weeks after delivery]: This outcome was assessed in pregnant participants after delivery.
• Number of Participants Diagnosed With a Hypertensive Disorder of Pregnancy [From time of GDM screen up to 6 weeks after delivery]: This outcome was assessed in pregnant participants.
• Length of Postnatal Stay From Delivery to Discharge [Up to 1 week after delivery]: Average number of days admitted in the hospital after delivery up to discharge
• Number of Participants Who Had a Postpartum Readmission [From initial hospital discharge up to 6 weeks post-partum]: This outcome was assessed in pregnant participants post-delivery.
• Number of Participants With Type 2 Diabetes Mellitus Diagnosis Post-partum [From time of delivery up to 6 weeks post-partum]: This outcome was assessed in pregnant participants after delivery.
• Mean Neonatal Birthweight [Day of delivery (Within approximately 2 hours after delivery)]
• Number of Neonates With Birth Weight More Than 4000 Grams [Day of delivery (Within approximately 2 hours after delivery)]
• Number of Neonates Considered Large for Gestational Age (LGA) [Day of delivery (Within approximately 2 hours after delivery)]: LGA refers to neonatal birth weight larger than the 90th percentile for gestational age.
• Number of Neonates Considered Small for Gestational Age (SGA) [Day of delivery (Within approximately 2 hours after delivery)]: SGA are infants whose weight is < the 10th percentile for gestational age.
• Number of Neonates Admitted to the Neonatal Intensive Care Unit (NICU) [Up to 28 days after delivery]
• Number of Neonates With Hyperbilirubinemia [Up to 28 days after delivery]
• Number of Neonates With Hypoglycemia [Up to 28 days after delivery]
• Number of Neonates Diagnosed With Respiratory Distress Syndrome [Up to 28 days after delivery]
• Number of Neonates Exclusively Breastfeeding at Time of Hospital Discharge [Up to 28 days after delivery]

Sex: Female, ages: 18 Years to any

Inclusion Criteria:

1. Pregnant patients 18 years and older
2. Singleton gestation
3. Pregnancy managed at Lucile Packard Children's Hospital (LPCH) Stanford outpatient obstetrics clinic
4. Planned delivery at Lucile Packard Children's Hospital (LPCH) Stanford Labor and Delivery unit

Exclusion Criteria:

1. Pregestational diabetes
2. Gestational diabetes diagnosed in the 1st trimester
3. Less than 18 years of age
4. Planned delivery outside LPCH
5. Diabetes medication use prior to pregnancy
6. Inability to give informed consent
7. Chronic steroid use in pregnancy
8. Less than 24 weeks of gestation at the time of the 1 hour oral glucose tolerance test
9. Prior history of bariatric surgery
10. Multifetal gestation

Participant flow

Outcome 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) (Primary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 31; Fed Before Gestational Diabetes Screen 13 (p 0.002)
• Mean Gestational Age at OGTT Screen (Secondary), Mean, weeks: Fasting Before Gestational Diabetes Screen 25.7 +/- 1.2; Fed Before Gestational Diabetes Screen 25.8 +/- 1.3
• Mean Glucose Level at the OGTT Screen (Secondary), Mean, mg/dL: Fasting Before Gestational Diabetes Screen 127.7 +/- 35.8; Fed Before Gestational Diabetes Screen 113.3 +/- 26.4
• Number of Participants With Positive GDM Diagnosis Based on the OGTT (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 8; Fed Before Gestational Diabetes Screen 2
• Average Time of Last Oral Intake Prior to the OGTT Screen (Secondary), Mean, hours: Fasting Before Gestational Diabetes Screen 10.7 +/- 3.0; Fed Before Gestational Diabetes Screen 1.4 +/- 0.9
• Number of Participants With Positive GDM Diagnosis (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 12; Fed Before Gestational Diabetes Screen 5
• Mean Gestational Age at Delivery (Secondary), Mean, days: Fasting Before Gestational Diabetes Screen 272 +/- 12; Fed Before Gestational Diabetes Screen 272 +/- 10
• Number of Participants Who Delivered Vaginally (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 67; Fed Before Gestational Diabetes Screen 53
• Number of Participants Who Delivered Via Operative Vaginal Birth (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 3; Fed Before Gestational Diabetes Screen 7
• Number of Participants Who Delivered Vaginally After a Prior Cesarean Section (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 2; Fed Before Gestational Diabetes Screen 1
• Number of Participants Who Delivered Via a Primary Cesarean Section (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 17; Fed Before Gestational Diabetes Screen 21
• Number of Participants Who Delivered Via a Repeat Cesarean Section (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 7; Fed Before Gestational Diabetes Screen 14
• Number of Participants Complicated by Shoulder Dystocia at Delivery (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 0; Fed Before Gestational Diabetes Screen 1
• Number of Participants Complicated by Third or Fourth Degree Perineal Laceration (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 2; Fed Before Gestational Diabetes Screen 4
• Number of Participants With Post-partum Hemorrhage (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 16; Fed Before Gestational Diabetes Screen 10
• Number of Participants Diagnosed With a Hypertensive Disorder of Pregnancy (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 22; Fed Before Gestational Diabetes Screen 15
• Length of Postnatal Stay From Delivery to Discharge (Secondary), Mean, days: Fasting Before Gestational Diabetes Screen 2.3 +/- 0.9; Fed Before Gestational Diabetes Screen 2.4 +/- 1.1
• Number of Participants Who Had a Postpartum Readmission (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 4; Fed Before Gestational Diabetes Screen 6
• Number of Participants With Type 2 Diabetes Mellitus Diagnosis Post-partum (Secondary), Count of participants, Participants: Fasting Before Gestational Diabetes Screen 1; Fed Before Gestational Diabetes Screen 0
• Mean Neonatal Birthweight (Secondary), Mean, grams: Fasting Before Gestational Diabetes Screen 3231 +/- 631; Fed Before Gestational Diabetes Screen 3268 +/- 458
• 8 more outcome measures not shown.

Adverse events

Time frame: Up to 22 weeks (from 24 weeks gestation up to 6 weeks post-partum)

Serious adverse events by term

• Results publication: Sperling MM, Leonard SA, Miller SE, Hurtado J, El-Sayed YY, Herrero T, Faig J, Carter S, Blumenfeld YJ. Fasting Compared With Fed and Oral Intake Before the 1-Hour Oral Glucose Tolerance Test: A Randomized Controlled Trial. Obstet Gynecol. 2023 Jan 1;141(1):126-133. doi: 10.1097/AOG.0000000000005013. Epub 2022 Nov 30. PMID 36701613

• Study Protocol (PDF, 2021-03-15)
• Statistical Analysis Plan (PDF, 2022-05-20)
• Informed Consent Form (PDF, 2021-03-15)

• Yair Blumenfeld, MD, Principal investigator, Associate Professor

NIH grants: P30DK116074