Gestational Diabetes (Priscilla White Class A DM)

Updated July, 2023

Contributor:  Division of Maternal-Fetal Medicine

Basics

Definition: insulin resistance arising during pregnancy that results in carbohydrate intolerance

Types: A1GDM (diet-controlled) and A2GDM (medication-controlled)

Prevalence: varies in direct proportion to the prevalence of T2DM in the population in a particular racial or ethnic group. Increasing globally with the increase in obesity and sedentary lifestyles in the U.S.

Screening

Universal screening for pregestational diabetes is recommended at the initial prenatal visit, in the form of a Hgb A1C (see algorithm for screening below).  The goal of early screening is to identify women who have pregestational diabetes.

 

Institutionally, we utilize the Carpenter and Coustan threshold values for GDM diagnosis, as follows:

• Fasting >95
• 1 hr > 180
• 2 hr > 155
• 3 hr > 140

 

Monitoring and Treatment – SEE ATTACHED ALGORITHM FOR MANAGEMENT OF GDM and PGDM

All women diagnosed with GDM should receive lifestyle modification counseling, specifically nutrition and activity counseling

The actual dietary composition that maximizes perinatal outcomes is unknown, but the following breakdown of macronutrients is recommended:

• Carbohydrates: 33-40%, preferably complex carbohydrates; avoid sugar-sweetened beverages
• Protein: 20%
• Fat: 40%

Women should eat 3 meals and 2-3 snacks per day (one snack close to bedtime) to maintain stable plasma glucose levels.  Meal/snack carbohydrate recommendations:

• Breakfast 15-30 grams of carbohydrate
• Lunch 30-60 grams of carbohydrate
• Dinner 30-60 grams of carbohydrates
• Snacks 15-30 gram of carbohydrate

Exercise/physical activity counseling

• 30 minutes of moderate aerobic exercise 5 days per week OR 150 minutes total per week is recommended to improve glycemic control

Glucose monitoring should occur 4 times daily: once fasting and again 2 hours after the first bite of each meal.  “Fasting” is defined as nothing to eat or drink (with the exception of water) for the 8 hours preceding the check.

               Target levels (per the American Diabetes Association 2024 Guidelines):

• Fasting < 95
• 2-hr post-prandial <120

Can consider continuous glucose monitor for patients who are not able to be compliant with fingersticks or for confirmation of glycemic control.

Patients should be seen in the office every 2-3 weeks to review logs. Logs should be reviewed at least weekly, either virtually or in the office, if glucose is poorly controlled or if patient is on medication

It is reasonable to allow a 1-2 week trial of dietary management before initiation of medication. Waiting longer does not increase the likelihood of good control after  dietary and lifestyle adjustments have been made.

Insulin therapy is first-line pharmacologic treatment of A2GDM

Utilize the Diabetes in Pregnancy Smartset for prescribing

Long acting insulins: Glargine (Lantus, Semglee, Basaglar) and Degludec (Tresiba) will impact fasting and pre-prandial values (if checked)

• NPH is second line secondary to the higher risk of hypoglycemic episodes

Rapid acting insulins: Aspart (Novolog) and Lispro (Humalog or Admelog) impact post-prandial values.  Avoid regular insulin.

               Dosing: Weight-based dosing based on trimester using actual (current) body weight

               TDI = Total Daily Insulin

• 1^st trimester: TDI = 0.7 units/kg/day
• 2^nd trimester: TDI = 0.8 units/kg/day
• 3^rd trimester: TDI = 0.9 units/kg/day

Divide the TDI dose into 50% long-acting insulin and 50% rapid acting insulin

• Long-acting (basal) insulin glargine should be divided to be dosed every 12 hours OR decludec can be dosed once daily.
• Rapid-acting (bolus) insulin should be divided into TID with meals

Example:             Patient weight 111kg at 32 weeks EGA. 

                              111 x 0.9 = 100 (this is the TDI)

                              50% TDI long-acting (50units/2:  25 units every 12 hours)

                              50% TDI short-acting (50 units/3:  16 units with meals)

Individualize the patient’s regimen based on need (ie some patients may only need long-acting insulin)

Insulin should be adjusted in 10-20% increments  every 3-7 days

Oral hypoglycemic agents are second-line treatment for GDM; however there is a use for them in women who decline insulin, who cannot afford insulin, or who cannot safely administer insulin

In these situations, patients must be counseled on the lack of safety data, particularly the lack of long-term neonatal follow-up, as well as high treatment failure requiring insulin administration

Metformin (preferred to glyburide)

• Dosing:
  • Starting: Metformin 500 mg BID with breakfast and dinner OR Metformin XR 1000 mg daily with a meal (NOTE: there is currently a black box warning for certain versions of Metformin XR – do not use until this is resolved)
  • Titrate slowly to minimize GI side effects
  • Maximum dose: 2550 mg/day

Glyburide

• Dosing
  • Starting: 2.5 mg PO BID with breakfast and dinner
  • Major risk is hypoglycemia, especially if not taken with a meal
  • Maximum dose: 20 mg per day

Two recent meta-analyses have demonstrated worse neonatal outcomes (RDS, hypoglycemia, macrosomia, birth injury) for glyburide compared to insulin despite no difference in overall glycemic control

               Hypoglycemia is defined as blood glucose is ≤ 62 mg/dL

                              Treat with 15 g of rapid acting carbs (Dex4, 4 glucose tabs, or 4 oz juice)

                              Recheck glucose in 15 minutes

                              Repeat treatment until glucose > 62 mg/dL

                              Once adequately treated, eat meal or protein snack

Instruct patients not to operate a motorized vehicle until blood glucose is >70 mg/dL, without symptoms of hypoglycemia, and at least 30 minutes after hypoglycemic episode due to delayed recovery of cognitive function

Fetal risks

• Macrosomia
• Stillbirth

Neonatal risks

• LGA
• Neonatal hypoglycemia
• Hyperbilirubinemia
• Shoulder dystocia
• Birth trauma
• Childhood and adult risks of obesity and T2DM

 

Maternal risks

• Preeclampsia
• Cesarean delivery
• Development of T2DM outside of pregnancy
• Pelvic trauma
• Preterm delivery

Ultrasounds

               Anatomic survey at 18-22 weeks

               At least one additional growth scan in A1GDM

               Serial growth scans at time of diagnosis of A2GDM

Antenatal testing

Risk of IUFD is increased with poor glycemic control during the pregnancy, and therefore antenatal testing is recommended in the setting of A2GDM.  This includes patients who have declined recommended medication for glycemic control.

Institutionally, we initiate twice-weekly testing (once weekly NST, once weekly BPP) at 32 weeks (earlier if multiple comorbidities or poor control).    

Delivery

               Timing (in the absence of other comorbidities)

                              A1GDM: 39w0d- 40w6d (with appropriate antenatal testing)

                              A2GDM: depends on control

• Good control: 39w0d – 39w6d
• Poor control: 37w0d – 38w6d, only sooner with abnormal antenatal testing or failed in-hospital glycemic control attempts

Mode

               Shared decision-making between patient and provider is essential in determining mode of delivery in patients with diabetes complicated by fetal macrosomia.   Counseling regarding the risks and benefits of scheduled cesarean delivery when the EFW is >4500g is recommended

Intrapartum management

               Discontinue entire home regimen if patient has A2GDM

Check blood sugars on admission and every 2 hours in active labor

               Utilize IV insulin infusion (insulin drip) if glucose >120 mg/dL

Postpartum considerations

Check fasting and 2 hr postprandial blood sugars in the immediate postpartum period off of medications (for patients who are in-house longer than 2-3 days, individualize need for fingersticks).

Schedule a 2-hr GTT at 6-12 weeks postpartum

Patient needs a PCP referral placed in the third trimester, as ACOG and the ADA recommend repeat testing every 1-3 years if initial postpartum screening is normal

• Consider Access Health referral for patients who will not have insurance beyond the immediate postpartum period
• Utilize the Physician Finder referral for those patients who will remain insured beyond the immediate postpartum period

Up to 70% of women with GDM will develop diabetes within 22-28 years of pregnancy