What is the management approach for a pregnant woman with diabetes mellitus (DM)?

Management of Diabetes Mellitus in Pregnancy

Insulin is the mandatory first-line pharmacologic therapy for all pregnant women with preexisting diabetes (type 1 or type 2) who cannot achieve glycemic targets with lifestyle modifications alone, as it does not cross the placenta and is the safest option for both mother and fetus. 1, 2

Preconception Planning and Optimization

All women with diabetes of childbearing age must achieve optimal glycemic control before conception to minimize the risk of congenital malformations, with a target A1C <6.5% (ideally <6%) prior to pregnancy. 1, 3

Critical Preconception Steps:

• Discontinue all teratogenic medications immediately when pregnancy is planned or detected, specifically ACE inhibitors, angiotensin receptor blockers, and statins 1, 2

• Initiate folic acid supplementation at 400 mg daily (some guidelines recommend up to 400-600 mg) to reduce neural tube defect risk 1, 3

• Complete comprehensive screening including:

  • A1C, thyroid-stimulating hormone (TSH), serum creatinine, and urinary albumin-to-creatinine ratio 1
  • Dilated ophthalmologic examination for retinopathy assessment 1, 3
  • Cardiovascular assessment if age ≥35 years or cardiac risk factors present 2
  • Screening for rubella, syphilis, hepatitis B, HIV, and cervical pathology 1

• Establish effective contraception until glycemic targets are achieved and all teratogenic medications are discontinued 1, 3

Multidisciplinary Team Approach:

Women with preexisting diabetes should be managed by a multidisciplinary team including an endocrinologist, maternal-fetal medicine specialist, registered dietitian nutritionist, and diabetes care and education specialist when available. 1, 2

Glycemic Targets During Pregnancy

Blood Glucose Targets:

The following strict glucose targets must be achieved to minimize maternal and fetal complications: 1, 3, 2

• Fasting glucose: <95 mg/dL (5.3 mmol/L) 1, 3
• 1-hour postprandial: <140 mg/dL (7.8 mmol/L) 1, 3
• 2-hour postprandial: <120 mg/dL (6.7 mmol/L) 1, 3

A1C Targets:

The optimal A1C target during pregnancy is <6% (42 mmol/mol) if achievable without significant hypoglycemia. 1, 3

• If hypoglycemia becomes problematic, the target may be relaxed to <6.5% (48 mmol/mol) or <7% (53 mmol/mol) as necessary 1
• A1C is physiologically lower in pregnancy due to increased red blood cell turnover 1

Glucose Monitoring Strategy

Both fasting and postprandial self-monitoring of blood glucose (SMBG) are mandatory for achieving metabolic control in pregnant women with diabetes. 1, 3

Monitoring Frequency:

• Women with preexisting diabetes on basal-bolus insulin or pump therapy must also perform preprandial testing to adjust rapid-acting insulin doses appropriately 1
• Postprandial monitoring is associated with better glycemic control and lower risk of preeclampsia compared to preprandial monitoring alone 1

Continuous Glucose Monitoring (CGM):

CGM should be used as an adjunct to, not a replacement for, SMBG in pregnant women with type 1 diabetes. 3, 4

• CGM reduces large-for-gestational-age births, neonatal hypoglycemia, and length of hospital stay in type 1 diabetes 3
• CGM improves glycemic control and reduces hypoglycemia risk when used in addition to SMBG 2, 4

Insulin Management

Insulin as First-Line Therapy:

Insulin is the preferred and mandatory medication for managing both type 1 and type 2 diabetes during pregnancy because it does not cross the placenta to a measurable extent. 1, 2, 4, 5

Insulin Delivery Methods:

Both multiple daily injections (MDI) and continuous subcutaneous insulin infusion (pump therapy) are appropriate delivery strategies, with neither proven superior. 1, 2, 4

• Physiologic basal-bolus regimens with rapid-acting insulin for meals and long-acting insulin for basal coverage are recommended 3, 4

Insulin Physiology Changes During Pregnancy:

Insulin requirements change dramatically throughout pregnancy and require frequent dose adjustments: 1, 4

• First trimester: Enhanced insulin sensitivity, lower glucose levels, and decreased insulin requirements 1, 4
• Second and third trimesters: Exponential increase in insulin resistance, with insulin requirements often doubling by the third trimester 1, 4
• Postpartum: Dramatic and immediate decrease in insulin requirements after placental delivery 1, 4

Insulin Dose Adjustments:

Insulin dosing must be adjusted based on blood glucose monitoring results, carbohydrate intake, physical activity levels, and stage of pregnancy. 4

• Regular evaluation of insulin requirements is necessary as pregnancy progresses, with adjustments typically needed every 2-3 weeks 4
• A rapid reduction in insulin requirements may indicate placental insufficiency and requires immediate medical evaluation 4

Medical Nutrition Therapy

Women with diabetes in pregnancy must consume consistent amounts of carbohydrates to match insulin administration and prevent glucose fluctuations. 1, 3, 4

• Referral to a registered dietitian nutritionist is essential to establish a food plan, insulin-to-carbohydrate ratio, and appropriate weight gain goals 2
• Regular moderate exercise is recommended as part of comprehensive lifestyle management 3

Prevention of Complications

Aspirin for Preeclampsia Prevention:

All pregnant women with diabetes should be prescribed low-dose aspirin 60-150 mg/day (usual dose 81 mg/day) by the end of the first trimester (12-16 weeks gestation) to reduce the risk of preeclampsia. 1, 2

Blood Pressure Management:

Target blood pressure during pregnancy is <135/85 mmHg, avoiding targets lower than 120/80 mmHg which may impair fetal growth. 1, 2

Retinopathy Monitoring:

Women with preexisting diabetic retinopathy require dilated eye examinations ideally before pregnancy or in the first trimester, then monitoring every trimester and for 1 year postpartum. 1, 3

• Rapid implementation of euglycemia in the setting of retinopathy is associated with worsening of retinopathy 1

Hypoglycemia Management

Education on hypoglycemia prevention, recognition, and treatment is mandatory for all pregnant women with diabetes and their family members. 1, 3, 4

• Women with type 1 diabetes have increased risk of hypoglycemia in the first trimester and altered counterregulatory response throughout pregnancy that may decrease hypoglycemia awareness 1
• Glucagon should be available to the patient and close contacts should be trained in its use 6

Diabetic Ketoacidosis (DKA) Prevention

Pregnancy is a ketogenic state, and women with type 1 diabetes are at risk for DKA at lower blood glucose levels than in the nonpregnant state. 1

• Women with type 1 diabetes should be prescribed ketone strips and receive education on DKA prevention and detection 1
• DKA carries a high risk of stillbirth 1
• Women in DKA who are unable to eat often require 10% dextrose with an insulin drip to adequately meet the higher carbohydrate demands of the placenta and fetus 1

Hypokalemia Monitoring

Potassium levels must be monitored closely when insulin is administered, particularly intravenously, as insulin stimulates potassium movement into cells and can cause life-threatening hypokalemia. 5

• Use caution in patients taking potassium-lowering medications or medications sensitive to serum potassium concentrations 5
• Untreated hypokalemia may cause respiratory paralysis, ventricular arrhythmia, and death 5

Labor and Delivery Management

During active labor, target plasma glucose levels are 80-110 mg/dL, and an intravenous insulin infusion is recommended to achieve these targets. 2, 7

• 10% glucose infusion should be administered alongside insulin to prevent maternal hypoglycemia and ketosis during labor's increased energy demands 2

Postpartum Management

Insulin requirements decrease dramatically immediately after placental delivery, requiring close monitoring and rapid dose reduction to prevent hypoglycemia. 1, 2, 4

• Reduce insulin to either 80% of pre-pregnancy doses or 50% of end-pregnancy doses immediately after delivery 2
• Target blood glucose 110-160 mg/dL after delivery 2

Breastfeeding Support:

All women with diabetes should be supported in breastfeeding attempts, as it provides immediate nutritional and immunological benefits to the baby and may confer longer-term metabolic benefits to both mother and offspring. 2

• Good glucose control supports lactation in patients with diabetes 5
• Patients who are lactating may require adjustments in insulin dose and/or diet 5

Contraception Planning:

A contraceptive plan, including discussion of long-acting reversible contraception, must be established with all women with diabetes of reproductive potential before hospital discharge. 1, 6

Management of Gestational Diabetes Mellitus (GDM)

GDM should be managed first with medical nutrition therapy and exercise, with insulin added if glucose targets are not achieved within 1-2 weeks. 1, 3

• Treatment of GDM improves perinatal outcomes, including reduced macrosomia and birth complications 3
• Women with GDM have increased risk of developing type 2 diabetes and require postpartum screening 3

Alternative Oral Agents for GDM:

For women with GDM who cannot safely or effectively use insulin due to cost, language barriers, comprehension, or cultural influences, oral agents (metformin or glyburide) may be considered as an alternative after discussion of known risks and need for more long-term safety data. 1

• Most oral agents cross the placenta or lack long-term safety data 1

Common Pitfalls to Avoid

• Failing to discontinue teratogenic medications (ACE inhibitors, ARBs, statins) before conception or immediately upon pregnancy detection
• Inadequate preconception glycemic optimization, leading to increased risk of congenital malformations with A1C >6.5%
• Insufficient insulin dose adjustments as pregnancy progresses, particularly in the second and third trimesters when insulin resistance increases exponentially
• Failure to reduce insulin doses immediately postpartum, leading to severe hypoglycemia
• Neglecting to monitor for and treat hypokalemia when using intravenous insulin
• Missing the window for aspirin initiation (should start by 12-16 weeks gestation for preeclampsia prevention)
• Inadequate hypoglycemia education for patients and family members, particularly in type 1 diabetes