Evaluation

Maternal Surveillance

Hyperglycemia Detection

The goal of maternal surveillance is to detect hyperglycemia and maintain good glycemic control throughout pregnancy to decrease maternal and fetal adverse outcomes. High maternal glucose increases the risk of higher frequency of primary cesarean section delivery, preterm delivery, preeclampsia, shoulder dystocia or birth injury, fetal macrosomia, fetal anomalies, neonatal hypoglycemia, neonatal hyperbilirubinemia or jaundice, neonatal respiratory distress syndrome, intensive neonatal care, spontaneous abortion, fetal demise, and type 2 diabetes, hypertension and obesity in the offspring later in life. Fasting, preprandial, and postprandial blood glucose monitoring is recommended in pregnant women with diabetes. Preprandial testing is recommended with Insulin pumps or basal-bolus therapy to guide adjustment of premeal rapid-acting Insulin doses.



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Self-monitoring of blood glucose (SMBG) and continuous glucose monitoring (CGM) are reasonable alternatives for glucose monitoring during pregnancy. Recommend daily SMBG over intermittent office monitoring. Continuous glucose monitoring, in addition to preprandial and postprandial blood glucose monitoring, can help reach A1c targets and can lessen macrosomia and neonatal hypoglycemia in pregnancy complicated by type 1 DM. The goal is to keep sensor glucose values within 3.5-7.8 mmol/L (63-140 mg/dL) for >70% of the day, with <4% below 3.5 mmol/L (<63 mg/dL), <1% below 3 mmol/L (<54 mg/dL), and <25% above 7.8 mmol/L (>140 mg/dL).

Glycemic targets for patients with gestational diabetes mellitus and pre-existing diabetes in pregnancy are as follows: 

 


 Goal 
 FPG, plus either <5.3 mmol/L (<95 mg/dL) 
 1-hour postprandial blood glucose <7.8 mmol/L (<140 mg/dL) 
2-hour postprandial blood glucose  <6.7 mmol/L (<120 mg/dL) 

A1c should be used as a secondary measure of pregnancy glycemic outcomes, and if it can be obtained without developing hypoglycemia. The target A1c level in pregnancy is <6% (<42 mmol/mol) as pregnancy continues but may consider <7% (<53 mmol/mol) if needed to prevent hypoglycemia. Due to altered red cell kinetics and glycemic changes in pregnancy, A1c levels may have to be monitored more frequently (eg monthly) than usual.

Other Monitoring



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Measure the blood pressure (BP), body weight, and urinary protein, and check for edema every prenatal visit to detect the development of preeclampsia. Prevention, recognition, and treatment of hypoglycemia are important to help prevent and manage hypoglycemia risk. Hypoglycemia thresholds include blood glucose <3.9 mmol/L (<70 mg/dL) and sensor glucose <3.5 mmol/L (<63 mg/dL). Regular retinal and renal assessment during pregnancy should be done. Monitor urine and/or blood ketones to confirm if diet is adequate. Starvation ketosis is common in pregnancy and may have detrimental effects on the fetus. Exclude diabetic ketoacidosis in the patient if she is ill or is hyperglycemic.

Fetal Surveillance

Fetal surveillance should be individualized based on the severity of hyperglycemia in the mother and the presence of risk factors. It is not recommended to routinely monitor fetal well-being before 38 weeks unless risk for fetal growth restriction exists; however, a more frequent fetal health assessment is recommended if comorbid factors are present. Mother should be taught to monitor fetal movement in the last 8-12 weeks of pregnancy and to report any reduction in movement. If GDM is diagnosed during the first trimester, it is recommended to do an ultrasound at 18-22 weeks to detect congenital anomalies. 



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Non-stress testing, contraction stress testing, and/or biophysical profile assessments should be recommended to patients with GDM with poor glycemic control and comorbid conditions. Assess fetal response to gestational diabetes mellitus by ultrasound measurement of fetal abdominal circumference during the second trimester and early third trimester and repeat every 2-4 weeks to guide management decisions. Lower goals for glycemic control may be recommended for bigger fetal abdominal circumference.  Initiate weekly fetal well-being assessment at 34-36 weeks if with pre-existing diabetes in pregnancy with or without comorbidities and poorly controlled GDM. Intensify fetal surveillance when pregnancy is beyond 40 weeks of gestation.

Other Considerations

Gestational diabetes mellitus is not an indication for cesarean delivery. Consider a scheduled cesarean delivery in case of fetal macrosomia to minimize the risk of birth trauma. GDM is also not a consideration for delivery before 37 weeks of gestation unless there is maternal or fetal compromise; early delivery should be guided by risk assessment. Patients with type 1 or type 2 diabetes without complications are advised to have an elective birth through labor induction or cesarean section if indicated between 37 and 38 weeks. Gestation past 38 weeks increases the risk of macrosomia. Women with gestational diabetes mellitus are advised to give birth not later than 40 weeks and are offered elective birth if they have not delivered by this time, though elective labor induction is not necessary in women with good glycemic control and no other obstetric indication.

Nonpharmacological

Preconception Counseling



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Ask about pregnancy intentions at each reproductive, diabetes, and primary care visit in individuals with diabetes who may become pregnant. Educate the patient on the risks of diabetes to both mother and fetus and the measures for risk reduction (eg lifestyle and behavioral modification, nutrition assessment, weight management, setting of glycemic goals and medication plan, comprehensive diabetes self-management education, and Folic acid supplementation). Women with prior GDM should receive preconception diabetes screening (including screening for diabetes comorbidities and complications) and care to manage hyperglycemia and prevent congenital malformations. Advise family planning and use of effective contraception until glycemic control is optimized for pregnancy.

Discuss optimal HbA1c levels for pregnancy (ie <6.5% or <48 mmol/mol) to reduce the risk of preeclampsia, macrosomia, congenital anomalies, preterm birth, and other complications (eg diabetic retinopathy). Dilated eye exams should be performed in women with pre-existing diabetes before pregnancy and in the first trimester, with follow-up in each trimester and for 1 year postpartum based on retinopathy severity and ophthalmology recommendations. Review medications for potentially harmful drugs and transition to safer alternatives before pregnancy to allow stabilization of glucose, weight, lipids, and blood pressure, particularly in sexually active individuals of childbearing potential who are not using effective contraception.

Medical Nutrition Therapy (MNT)  

Medical nutrition therapy is the cornerstone of gestational diabetes mellitus management. Preconception care should be accessible to all females with pre-existing DM to ensure adequate nutrition and glucose control prior to conceiving, during pregnancy, and postpartum. This is best prescribed by a registered dietitian or a healthcare provider with experience in managing patients with GDM. The patient should be counseled about individual MNT based on their height and weight. Medical nutrition therapy should include adequate calories and nutrition to meet the needs of the mother and fetus. 



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For all pregnant individuals, the recommended daily dietary intake is at least 175 g carbohydrate, 71 g protein, and 28 g fiber. More complex and nutrient-dense carbohydrates, more fiber, lean protein, oily fish, vegetables, fruits, legumes, whole grains, nuts, seeds, and a balance of polyunsaturated fats and monounsaturated fats are recommended. Carbohydrate reduction to 35-40% of daily energy intake has been shown to decrease hyperglycemia and improve maternal and fetal outcomes. Limit consumption of processed foods, fatty red meat, saturated fats, and sweetened foods and beverages; avoid trans fats. Obese patients may benefit from calorie restriction (approximately 25 kcal/kg actual body weight/day). This is shown to decrease hyperglycemia and triglycerides and does not seem to increase ketonuria.

Avoid inappropriate weight loss or gain and avoid ketonuria. The recommended weight gain during pregnancy for overweight women is 6.8-11.3 kg and 4.54-9.1 kg for obese women. Consider testing for fasting urine ketones in individuals managing their blood glucose with severe carbohydrate restriction. This should be adjusted to meet glycemic control goals. If MNT fails to meet glycemic control goals within 1-2 weeks, Insulin administration should be considered.

Physical Activity 



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Physical activity is encouraged unless medical or obstetrical contraindication exists or glycemic control is worsened by activity. Pregnant and postpartum individuals should engage in at least 150 minutes of moderate-intensity aerobic activity weekly, ideally spread over 3-5 days, with about 30 minutes daily shown to lower maternal glucose levels. Examples of moderate physical activity include brisk walking, water aerobics, stationary cycling, and household chores. 

Pharmacological therapy

Insulin Preparations



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Insulin is the first-line pharmacotherapy recommended for gestational diabetes mellitus when lifestyle change or medical nutrition therapy fails to maintain glycemic control. This is also given to women with gestational diabetes mellitus when Metformin is contraindicated or unacceptable to the patient. Human insulin should be used in pregnant women because it is the least immunogenic. Rapid-acting insulin analogs develop antibodies similar to human insulin. Insulin with low antigenicity minimizes transplacental transport of insulin antibodies. Currently available human insulin preparations have been shown to not cross the placenta. A multidose regimen of Insulin administration may be needed for better control of blood glucose levels. This may be given as multiple daily injections or continuous subcutaneous infusion.

For pregnant individuals with type 1 diabetes, automated insulin delivery (AID) systems with pregnancy-specific glucose targets are recommended; AID systems without pregnancy-specific targets may be considered in select cases with assistive techniques and expert guidance. This includes hybrid closed-loop (HCL) pumps, which automatically adjust basal insulin delivery to keep levels in range, and partial closed-loop systems (eg predictive low-glucose suspend [PLGS] technology), which automatically suspend insulin delivery when low glucose is predicted. Individualize therapy and regularly adapt to the changing needs of pregnancy to meet glycemic control goals. The exact time course of each Insulin will depend on each particular preparation, the presence of antibodies in the patient, and the site of injection. Immediate treatment with Insulin, with or without Metformin, is considered in women with gestational diabetes mellitus who have a fasting plasma glucose of 6-6.9 mmol/L with complications (eg macrosomia or hydramnios) and is offered to women with gestational diabetes mellitus who have a fasting plasma glucose of ≥7 mmol/L at diagnosis.


INSULIN PREPARATIONS*
Drug Onset of Action (hr) Peak Effect (hr) Duration of Action (hr)
Rapid-Acting
Insulin aspart 10-20 min 1-3 3-5
Insulin lispro 15-30 min 0.5-2 3-5
Short-Acting
Insulin regular 0.5 1.5-3.5 4-8
Intermediate-Acting
Insulin isophane (NPH) 1-2 4-12 Up to 24
Long-Acting
Insulin detemir 3-4 3-9 24
Insulin glargine 3-6 No peak 24

*Please see Insulin Preparations clinical reference table for further information.

Metformin

Metformin may be given to women with a history of gestational diabetes mellitus and prediabetes but is not recommended as a first-line therapy. This may also be given if diet and exercise within 1-2 weeks failed to meet blood glucose targets and for patients not in their first trimester who cannot use or refuse Insulin or Glibenclamide. Metformin may be used as an alternative in some women who may not be able to use Insulin safely or effectively due to cost, comprehension, or cultural factors, but only after thorough discussion of known risks and the need for more data on long-term safety in offspring. This may be given with intensive lifestyle modification in postpartum women with a history of gestational diabetes mellitus who were found to have prediabetes. Metformin delays or prevents progression to diabetes in women with a history of gestational diabetes mellitus and prediabetes.

Metformin crosses the placenta, but the risk of neonatal hypoglycemia and maternal weight gain may be lower than with Insulin. This should be stopped by the end of the first trimester if used to treat PMOS and induce ovulation. Metformin should not be given to pregnant women with hypertension, preeclampsia, or with risk for intrauterine growth restriction due to the potential for growth restriction or acidosis in the setting of placental insufficiency. The initial dose is 500 mg orally once daily with food, titrated up to a max dose of 2.5-3 g/day. Long-term safety data for offspring is of some concern.

Glibenclamide (Glyburide)

Glibenclamide may be used as an alternative for patients with gestational diabetes mellitus who are unable or unwilling to take Insulin, who cannot tolerate Metformin, or whose blood glucose targets are not met with Metformin but refuse Insulin. This may be used as an alternative in some women who may not be able to use Insulin safely or effectively due to cost, comprehension, or cultural factors, but only after thorough discussion of known risks and the need for more data on long-term safety in offspring. Glibenclamide is a useful adjunct to MNT and physical activity regimens when additional treatment is necessary to maintain appropriate glucose levels. This is safe and effective in controlling glucose levels in >80% of patients with gestational diabetes mellitus. This has been shown to cross the placenta and is associated with a higher rate of neonatal hypoglycemia, macrosomia, and increased neonatal abdominal circumference compared to Insulin or Metformin. The initial dose is 2.5 mg orally once daily before meals, titrated up to a max dose of 20 mg/day. Long-term safety data for offspring is of some concern.