Gestational DM

GESTATIONAL DIABETES
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Dr/AL SAYED ALSPAGH Page | 1
Diabetes in Pregnancy
Diabetes mellitus (DM) can occur during pregnancy in 2 forms:
1) Pre-gestational (Pre-existing or Overt ) diabetes,
2) Gestational diabetes.
Pre-gestational diabetes: is defined as Type I or Type II DM that existed before
conception.
Gestational diabetes mellitus (GDM): is defined as glucose intolerance that is first
detected during the pregnancy and is associated with a probable resolution after the end
of the pregnancy.
GDM accounts for 90% of cases of diabetes in pregnancy while pre-gestational DM
accounts for 10% of such cases (T2D about 8 % and T1D about 2 %).
Pre-gestational diabetes represents very high-risk obstetrics. Women with pre-gestational
diabetes require careful and frequent monitoring for mother and fetus to identify and
anticipate complications. By contrast, GDM confers a much lower risk for both the mother
and fetus.
Pathophysiology of Gestational Diabetes
Pregnancy is a diabetogenic state. Normal pregnancy is characterized by pancreatic β-cell
hyperplasia resulting in higher fasting and postprandial insulin levels. Increased secretion
of placental hormones (e.g. Human placental lactogen) leads to increasing insulin
resistance, especially throughout the third trimester. GDM occurs when β-cell function is
insufficient to overcome this insulin resistance.
Screening for diabetes mellitus during pregnancy
A) Screening and diagnosis of GDM
The current recommendations from the ADA are to conduct a risk assessment for all
pregnant women at the first prenatal visit.
Women who are at very high risk should undergo testing as soon as possible, in order to
identify those with occult pre-existing type 2 diabetes (using the standard diagnostic
approach to diabetes).
Criteria for very high risk are as follows:
 Severe obesity
 GDM during a previous pregnancy or delivery of an LGA infant
 Presence of glycosuria
 Diagnosis of polycystic ovarian syndrome (PCOS)
 Strong family history of type 2 diabetes

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All pregnant women should be screened for gestational diabetes at 24-28 weeks
gestation—including those with negative test results in the first trimester—unless they are
at low risk.
To be considered at low risk, a woman must meet all of the following criteria:
 Age < 25 years
 Weight normal before pregnancy
 Member of an ethnic group with a low prevalence of diabetes
 No known diabetes in first-degree relatives
 No history of abnormal glucose tolerance
 No history of poor obstetric outcome
The best method for screening for GDM continues to be controversial. In updated
guidelines, the ADA 2020 recommends use of either the 1-step or the 2-step screening
method, advising that both tests are acceptable:
1) 2-step approach: A 50-g, 1-hour glucose challenge test (GCT) is followed by a 100-g,
3-hour OGTT for those with an abnormal screening result.
2) 1-step approach: can be used for high-risk women by proceeding directly to the 75-g,
2-hour OGTT without GCT.
A) Two-step approach
Step 1:
Perform a 50-g GCT (nonfasting), If the plasma glucose level measured 1 h after the
load is >130 mg/dL, proceed to a 100-g OGTT.
Step 2:
The 100-g OGTT should be performed when the patient is fasting and at 1, 2 and 3 h.
The OGTT should be performed in the morning after an overnight fast of at least 8 h.
 Fasting: 95 mg/dL
 1 h: 180 mg/dL two values are needed to diagnose GDM.
 2 h: 155 mg/dL
 3 h: 140 mg/Dl
A) One-step approach
Perform a 75-g OGTT, with plasma glucose measurement when patient is fasting and
at 1 and 2 h. The OGTT should be performed in the morning after an overnight fast of
at least 8 h.
 Fasting: 92 mg/dL
 1 h: 180 mg/Dl One value is needed to diagnose GDM.
 2 h: 153 mg/dL

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The American College of Obstetricians and Gynecologists (ACOG) prefer the 2-step
screening approach over the 1-step approach.
The GCT can be performed without regard to recent food intake (ie, non-fasting state).
The 50-g oral GCT < 130 mg/dL and/or FBS < 85 mg/dL are effective for ruling out the
presence of GDM.
The ADA does not consider a value > 200 mg per dL on a 50-g oral GCT to be diagnostic
of GDM; however, it is reasonable to treat these patients empirically as if they have GDM
(without performing a 100-g oral glucose tolerance test) because they require insulin
during pregnancy more often than patients with GDM diagnosed using the 100-g test.
Other tests (eg, HbA1C, RBS, or fructosamine level) are not recommended because of
low sensitivity for GDM.HbA1c levels fall during pregnancy and may not capture PPG.
B) Screening for Pre-gestational diabetes (T1D, T2D) and Pre-diabetes.
Standard diagnostic criteria for diagnosis of Overt (T1D or T2D) diabetes rather than
GDM by presence of any one of the following criteria:
1) HbA1C ≥ 6.5%
2) FPG ≥ 126 mg/dL; fasting is defined as no caloric intake for at least 8 hours*
3) 2-hour PPG ≥ 200 mg/dL; during a 75-g OGTT*
4) RBS ≥ 200 mg/dL; with classic symptoms of hyperglycemia.
* For 2h-PPG; give 75 g glucose dissolved in 300 ml water after overnight fasting in persons
who have been receiving at least 150-200 g of CHO daily for 3 days before the test.
 In patients without hyperglycemic symptoms, two abnormal test results of the first 3 tests,
needed to diagnose diabetes or repeated one test on a different day.
 In patients with hyperglycemic symptoms and RBS ≥ 200 mg/dL are diagnostic for DM
and no need for additional or repeated tests.
Prediabetes is a term used to distinguish people who are at increased risk of developing
diabetes. People with prediabetes have impaired fasting glucose (IFG) or impaired
glucose tolerance (IGT) or both.
Criteria defining prediabetes:
1) FPG 100-125 mg/dL (IFG) or
2) 2-hour PPG 140-199 mg/dL; during a 75-g OGTT (IGT) or
3) HbA1C 5.7–6.4%
Women with prediabetes identified before pregnancy should be considered at extremely
high risk of developing GDM. As such, they should receive early (first-trimester) diabetic
screening.

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Adverse Effects Associated with Gestational Diabetes Mellitus
Maternal Fetal
 Development of type 2 diabetes
 Gestational hypertension
 Preeclampsia
 Cesarean delivery
 Shoulder dystocia/birth trauma
 Macrosomia
 Birth defects
 Hyperbilirubinemia
 Metabolic complications e.g. Hypoglycemia,
hypomagnesemia, polycythemia,…
Macrosomic baby born to diabetic mother Shoulder dystocia born to diabetic mother
Management of Gestational DM
Benefits
Treating GDM results in decrease the incidence of preeclampsia, shoulder dystocia, and
macrosomia.
Blood sugar Targets
The target glucose levels to be maintained during diabetic pregnancy should be designed
to limit macrosomia or to closely mimic nondiabetic pregnancy profiles. The Fifth
International Workshop Conference on GDM recommends the following:
 FBS < 100 (90-99 mg/dL) and
 1-hour OGTT < 140 mg/dL or
 2-hour OGTT < 127 mg/dL

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Life style modification (Diet control and Exercise)
A) Diet control
The goal of dietary therapy for GDM is to avoid single large meals and foods with a large
percentage of simple carbohydrates.
American Diabetes Association (ADA) recommends that total calories during pregnancy
should comprised of 40% to 50% carbohydrates, including high-fiber fruits and starches
and milk if tolerated; 20% protein; and 35% fat.
ADA recommends a specific Medical nutrition therapy (MNT) for patients with GDM:
 Limit carbohydrate intake to 35% - 45% of total calories, distributed in 3 small to
moderate-sized meals and 2-4 snacks including an evening snack.
 Diet should contain 175g/day of digestible carbohydrate,1.1g/kg/day of protein and
enough fiber intake (28g/day), in form of vegetables, fruits, and whole grains.
 Fat consumption should be limited to < 30% of the total calories. Consumption of
unsaturated fatty acids including the n-6 and n-3 fatty acids should be encouraged;
saturated fat should be limited to <10% of energy intake and trans fats to the minimal
amount possible.
 Reduce folic acid dose to 0.4-1 mg from 5 mg at 12 weeks of gestational age.
 Women are encouraged to acquire micronutrients from natural food sources, but a
prenatal supplement of vitamins and minerals should be considered in women with
pre-existing diabetes.
 Vegetarian pregnant women may need supplements of vitamin D and vitamin B12.
B) Exercise
Exercise not only increases insulin sensitivity and improves glycemic control in GDM
women but also reduces the production of counter regulatory hormones. Furthermore it
has been shown that routine physical activity during pregnancy reduces adverse fetal or
maternal outcomes. The generally accepted recommendation is daily moderate-intensity
regular exercise (walking 30 minutes/day or more—if no medical contraindications)
Exercise also helps in weight management during pregnancy. Weight gain during
pregnancy is natural, however excessive weight gain is associated with maternal and fetal
complications.
American Diabetes Association recommends that pregnant women without any obstetrical
or medical contraindications, should be encouraged to do at least 30 minutes of physical
activity daily as a part of their overall diabetes management.

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Various exercises reported to be safe during pregnancy include:
 Aerobic exercises (bicycling, jogging, walking, stair climbing, treadmill use, water exercise, swimming),
 Progressive resistive strengthening,
 Stretching exercises,
 Yoga, and Qi.
The effect of aerobic exercise on reducing blood glucose levels lasts for more than 24 hours
but less than 72 hours.
However, some forms of exercises are not recommended during pregnancy. These include:
 Recreational sports with forceful contact or falling (basketball, rugby, horse riding and gymnastics).
 Exercising in a supine position after the first trimester (may obstruct IVC flow).
 Motionless standing and scuba diving (risk of fetal decompression sickness).
 Exercises that cause mild abdominal trauma (jarring motions or rapid changes in direction).
 High impact activities that require extensive jumping, hopping, skipping, or bouncing
 Deep knee bends, full sit-ups, double leg raises and straight-leg toe touches but it has
been shown that squatting after 36 weeks of gestation helps in vaginal delivery.
 Bouncing while stretching.
Oral Medications
Although insulin has historically been the standard therapy for women with uncontrolled
GDM due to its efficacy and safety. Oral medications are now appropriate first-line
therapies especially if the patient refuses Insulin or there were contraindications to use
insulin.
Options for oral medications include metformin and glyburide (glibenclamide). Although
neither glyburide nor metformin has been approved by the FDA for the treatment of GDM,
both are pregnancy category B. Metformin and glyburide cross the placenta but have not
been associated with birth defects or short-term adverse neonatal outcomes, although
the potential for long-term adverse effects remains a concern.
Metformin is typically started at 500 mg once daily with food, and titrated to a maximum
dosage of 2,500 mg per day (given in divided doses with meals).
Glyburide is initiated at 2.5 mg once per day one hour before eating, and increased to a
maximum of 10 mg twice per day, as needed. Between 15% and 40% of women initially
prescribed oral medications for GDM ultimately require insulin.
Insulin
Insulin is indicated for GDM management when (FIGO):
 Uncontrolled blood glucose after 2 weeks of lifestyle changes and use of oral medications,
 In women who elect to avoid a trial of oral medications.
 One of the risk factors:
 Diagnosing diabetes before 20 weeks of gestation
 Oral therapy for more than 30 weeks
 Fasting plasma blood glucose above 110 mg/dl

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 1-hour postprandial glycemia above 140 mg/dl
 Weight gain over 12 kilograms during pregnancy
Insulin does not cross the placenta; rapid-, intermediate-, and long-acting insulins are
considered safe for use in pregnancy.
Insulin regimens and calculating Insulin dosages:
Dosage monitoring and administration regimens are adjusted based on individual
response to nutrition interventions, exercise and insulin administration techniques.
Multiple daily injections provide the most optimal control during pregnancy.
One approach to starting insulin therapy is to calculate a total daily dosage of 0.7 to 1.0
units per kg.
Suggested Starting Total Daily Insulin during Pregnancy:
Weeks of Gestation Total Daily Insulin
1st Trimester 0.7 units/kg/day,
2nd Trimester 0.8 units/kg/day,
3rd Trimester 0.9–1.0 units/kg/day.
Usually, the calculated total daily dose of insulin should be divided in two as for type 1
and type 2 diabetes: Half of is administered as a single dose of long-acting insulin (e.g.,
glargine, detemir) at bedtime, and the other half is administered in three divided doses at
mealtimes as rapid-acting insulin (e.g., lispro, aspart).
Usually, in pre-gestational diabetes (type 1 and 2), the total insulin dose is up to twice
higher than in GDM.
In the case of morbid obesity, the initial doses of insulin can be increased to 1.5–2.0
units/kg to overcome the combined IR of pregnancy and obesity
Insulin dosing should be individualized and adjusted as needed for example:
Total daily dose (TDD) of Insulin
50% basal 50% bolus
(given at bedtime) (divided into 3 meals)
Monitor FBS Monitor 1-hour or 2-hour PPG
Average FBS > 99 mg/dl Average 1-h PPG > 140 OR 2-h PPG >127 mg/dl
Basal Insulin by 2-4 IU Prandial Insulin doses by 2-4 IU

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Peripartum management
Prenatal and intranatal management:
Various fetal biophysical tests can ensure that the fetus is well oxygenated, including fetal
heart rate testing, fetal movement assessment, ultrasonographic biophysical scoring, and
fetal umbilical Doppler studies.
Regular Insulin is withheld during labor; a sliding scale of soluble insulin should be started
(or infusion pump as may be fit).
Maternal hyperglycemia should be avoided during labor to prevent fetal hyperinsulinemia
and subsequent neonatal hypoglycemia.
Maintain maternal blood sugars between 70 and 110 mg/dl with a mean intrapartum
glycemic value of 100 mg/dl.
Management of the neonate:
Current recommendations for infants of diabetic mothers—the most critical metabolic
problem for whom is hypoglycemia— include the employment of frequent blood glucose
checks and early oral feeding (ideally from the breast) when possible, with infusion of
intravenous glucose if oral measures prove insufficient.
Postnatal management:
Patients with GDM usually do not need insulin, and women with type 1 and type 2
diabetes return to the previous regimen.
Before discharge, it is reasonable to confirm that fasting glucose values are normal.
Women with GDM should undergo screening for DM at 6-12 weeks postpartum with FBS
and PPG then every three years.
GDM is a significant risk factor for subsequent development of diabetes, where 36% of
women with GDM develop T2D soon or later.
Breastfeeding may reduce the subsequent risk of developing type 2 diabetes in women
who had GDM.

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Algorithm for Management of GDM (adapted from AAFP)
Presentation for antenatal care
Risks for preexisting diabetes mellitus?
NO Yes
Screen for diabetes using
FBS, HbA1c level, or 2-hour OGTT
Normal Abnormal
Screen at 24-28 weeks for GDM Manage as
pre-existing DM
Normal Abnormal
Routine care Begin life style Modification (Diet control and exercise)
with close follow-up by OGTT
Continue monitoring Controlled Not controlled
Consider initiation of oral agent or insulin
and follow-up after 1-2 weeks
Continue the same management Controlled Not controlled
Initiate and/or intensify therapy (Insulin)
Consider antenatal testing at 32-34 weeks
Poor glycemic control despite medication use
or another indication for delivery (such as preeclampsia) exists?
Yes NO
Plan for delivery in time Induction of labor
No Estimated fetal weight > 4,500 g YES
Vaginal birth cesarean delivery
Generally discontinue oral agents and/or insulin after delivery and Screen blood sugar
at 6-12 weeks postpartum then every three years.

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REFERENCES
1. American Diabetes Association. Standards of medical care in diabetes—2020.
2. American College of Obstetricians and Gynecologists. Committee on practice bulletins—Obstetrics. ACOG practice
bulletin No. 190: Gestational diabetes mellitus. Obstetrics and Gynecology. 2018;
3. Diabetes in Pregnancy: Management from Preconception to the PostnatalPeriod NICE Guideline. 2015.
4. Am Fam Physician. 2015 Apr 1;91(7):460-467.
5. International Association of Diabetes and Pregnancy Study Groups Consensus Panel, Metzger BE, Gabbe SG,
Persson B, Buchanan TA, Catalano PA, et al. International association of diabetes and pregnancy study groups
recommendations on the diagnosis and classification of hyperglycemia in pregnancy. Diabetes Care. 2010;33: 676-
682. PMID: 20190296
6. National Institutes of Health consensus development conference statement: diagnosing gestational diabetes
mellitus, March 4-6, 2013. Obstet Gynecol. 2013;122.
7. Benefits and harms of treating gestational diabetes mellitus: a systematic review and meta-analysis for the U.S.
Preventive Services Task Force and the National Institutes of Health Office of Medical Applications of Research.
Ann Intern Med. 2013; 159(2): 123-129.
8. Safety of insulin glargine use in pregnancy: a systematic review and meta-analysis. Ann Pharmacother.
2011;45(1):9-16.
9. Efficacy, safety and lack of immunogenicity of insulin aspart compared with regular human insulin for women with
gestational diabetes mellitus. Diabet Med. 2007;24(10):1129-1135.
10. Detemir in Pregnancy Study Group. Maternal efficacy and safety outcomes in a randomized, controlled trial
comparing insulin detemir with NPH insulin in 310 pregnant women with type 1 diabetes. Diabetes Care. 2012;
35(10): 2012-2017.
11. Glibenclamide, metformin, and insulin for the treatment of gestational diabetes: a systematic review and meta-
analysis. BMJ 2015; 350: h102.
12. Insulin Use in Pregnancy: An Update. Diabetes Spectrum 2016; 29(2): 92-97.
13. The International Federation of Gynecology and Obstetrics (FIGO) Initiative on gestational diabetes mellitus: A
pragmatic guide for diagnosis, management, and care. International Journal of Gynecology &Obstetrics. 2015;13
14. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3830373/
15. https://www.intechopen.com/books/gestational-diabetes-mellitus-an-overview-with-some-recent-advances/insulin-
therapy-in-gestational-diabetes
16. ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists. Number 60, March 2005.
Pregestational diabetes mellitus.
17. Gestational diabetes and the incidence of type 2 diabetes: a systematic review. Diabetes Care. 2002;25.
18. Long-term protective effect of lactation on the development of type 2 diabetes in women with recent gestational
diabetes mellitus. Diabetes. 2012
Prepared by:
Dr/ALSAYED ALSPAGH,
MSc, internal medicine
Consultant of internal medicine, Aim’s clinic, Maldives

Gestational DM

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