Diabetes in Pregnancy

DIABETES MELLITUS IN PREGNANCY

• Most common medical complication of pregnancy.
• Gestational Diabetes Mellitus (GDM): occurs in 4% of pregnancies.
• Pregestational Diabetes (Type 1 or Type 2): affects ~0.5% of pregnancies.

Importance of Glycemic Control

• Poorly controlled diabetes → high risks for:
  • Spontaneous abortion
  • Major congenital malformations
  • Preterm birth
  • Preeclampsia
  • Stillbirth
• Pathophysiology: maternal hyperglycemia → fetal hyperglycemia → fetal hyperinsulinemia → increased fetal growth (macrosomia).

Fetal Macrosomia

• Definition: fetal birth weight >4500 g.
• Leads to delivery complications (e.g., shoulder dystocia) and risk of birth trauma.

PHYSIOLOGIC CHANGES & DIAGNOSIS

Normal Pregnancy Glucose Metabolism

1. First Trimester: rising estrogen & progesterone → ↓ fasting plasma glucose (by ~15 mg/dL).
2. Second & Third Trimesters: increased human chorionic somatomammotropin (hCS) or human placental lactogen → growth hormone–like action that promotes lipolysis and antagonizes insulin → mild hyperglycemia.

Definitions for Diabetes in Pregnancy

• Pregestational diabetes (type 1 or 2) follows standard diagnostic criteria.
• Gestational Diabetes Mellitus (GDM): hyperglycemia first recognized during pregnancy.

Screening & Testing

• Universal screening recommended between 24–28 weeks gestation.
• Earlier screening if high risk (BMI >30, history of GDM, prior infant with malformation, or strong family history of diabetes).

One-Step Approach

• 50-g Oral Glucose Challenge Test (GCT):
  • Measure plasma glucose at 1 hour.
  • If >130 mg/dL (some use 140 mg/dL), proceed to 3-hour 100-g Oral Glucose Tolerance Test (OGTT).

Diagnostic 3-hour 100-g OGTT

• GDM confirmed if ≥2 of these plasma glucose values are met/exceeded:
  • Fasting: ≥95 mg/dL
  • 1 hour: ≥180 mg/dL
  • 2 hours: ≥155 mg/dL
  • 3 hours: ≥140 mg/dL
• Exception: If 1-hour GCT >180 mg/dL and fasting >95 mg/dL, GDM is confirmed without needing the OGTT.

MANAGEMENT OF GDM

Lifestyle Therapy

1. Daily exercise (as tolerated).
2. Nutrition therapy with calorie allotment, mild carbohydrate restriction (33–40% of total calories).
3. Self-monitoring of blood glucose (SMBG) ≥4 times/day (fasting + postprandial).

Glycemic Targets in Pregnancy

• Fasting plasma glucose: 70–95 mg/dL
• 1–2 hour postprandial glucose: <120 mg/dL

Pharmacotherapy

• About 15% of GDM patients require insulin if lifestyle alone isn’t enough.
• Insulin dosing individualized to meet above glucose targets.

Monitoring Pregnancy

• Ultrasound for fetal growth, amniotic fluid volume.
• Evaluate & treat:
  • Hypertension/preeclampsia
  • Diabetic retinopathy (especially in pregestational diabetes)
  • Ketoacidosis
  • Urinary tract infections

Postpartum & Future Risk

• Glucose often returns to normal postpartum in GDM patients, but:
  • 60% risk of GDM recurrence in subsequent pregnancies.
  • 50% develop type 2 diabetes in next 10 years.

LONG-TERM EFFECTS ON OFFSPRING

• Fetal hyperinsulinemia & excess fat deposits in utero → linked to:
  • Childhood obesity
  • Insulin resistance
  • Future impaired glucose tolerance or diabetes as adults.