Chapter 491: Medical Disorders During Pregnancy¶
Medical Disorders During Pregnancy | Part 19: Consultative Medicine
KEY CLINICAL POINTS¶
- Hypertension during pregnancy is classified as preeclampsia, gestational hypertension, or chronic hypertension based on timing and associated features.
- Gestational diabetes mellitus (GDM) affects ~8% of pregnancies and requires screening with a 50-g glucose challenge test followed by a 100-g oral glucose tolerance test.
- Preeclampsia management prioritizes delivery of the fetus and placenta, with antihypertensive therapy (labetalol, hydralazine) for severe hypertension.
- Maternal mortality is influenced by cardiovascular disease, hemorrhage, and infections, with significant racial disparities in outcomes.
- Multidisciplinary care involving internists, maternal-fetal medicine specialists, and other subspecialists is critical for managing complex pregnancies.
1. DEFINITION & OVERVIEW¶
Classification of Hypertension During Pregnancy¶
| Category | Definition | Key Features |
|---|---|---|
| Preeclampsia | New-onset hypertension ‡140/90 mmHg after 20 weeks with proteinuria or end-organ damage | Severe features: systolic ‡160/110 mmHg, thrombocytopenia, renal insufficiency |
| Gestational Hypertension | Elevated BP ‡140/90 mmHg after 20 weeks without proteinuria | No end-organ damage; risk of progressing to preeclampsia |
| Chronic Hypertension | Preexisting hypertension before 20 weeks | Risk of superimposed preeclampsia and placental complications |
Gestational Diabetes Mellitus (GDM) Diagnostic Criteria¶
| Test | Fasting Glucose | 1h Postload | 2h Postload |
|---|---|---|---|
| OGTT | <95 mg/dL | <180 mg/dL | <155 mg/dL |
| Alternative | ‡130 mg/dL | ‡190 mg/dL | ‡130 mg/dL |
1.1 Hypertension in Pregnancy¶
Hypertension during pregnancy is classified as preeclampsia, gestational hypertension, or chronic hypertension. Preeclampsia is defined by new-onset hypertension ≥ 140/90 mmHg after 20 weeks gestation with proteinuria or end-organ damage.
1.2 Diabetes in Pregnancy¶
Diabetes mellitus in pregnancy includes pregestational diabetes (type 1 or 2) and gestational diabetes mellitus (GDM). GDM is diagnosed via oral glucose tolerance testing (OGTT) and is associated with increased risks of macrosomia and cesarean delivery.
2. EPIDEMIOLOGY¶
Approximately 3.7 million births occur annually in the U.S., with ~130 million globally. Hypertensive disorders affect 16% of U.S. deliveries, and GDM occurs in ~8% of pregnancies. Obesity (OR 2.2 vs 0.5 for normal weight) and preexisting diabetes increase risks.
2.1 Preeclampsia¶
5–7% of pregnancies develop preeclampsia. Risk factors include nulliparity, advanced maternal age, and preexisting hypertension. Prevalence is rising due to increased maternal age and obesity.
2.2 Gestational Diabetes¶
GDM occurs in ~8% of pregnancies. Risk factors include obesity, family history of diabetes, and previous GDM. Ethnic disparities exist, with higher rates in Hispanic, Black, and Native American populations.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
Preeclampsia is linked to placental ischemia, maternal inflammation, and angiogenic imbalance (sFlt-1/PlGF ratio ≥ 40). Gestational diabetes results from insulin resistance due to placental hormones. Obesity exacerbates insulin resistance and metabolic stress.
3.1 Preeclampsia Pathogenesis¶
Chronic uteroplacental ischemia, exaggerated maternal inflammation, and imbalance of angiogenic factors (sFlt-1/PlGF ≥ 40) contribute to preeclampsia. Placental dysfunction leads to systemic endothelial activation.
3.2 Gestational Diabetes¶
Insulin resistance from placental hormones (glucocorticoids, lactogen) and reduced insulin sensitivity in adipose tissue drive hyperglycemia. Obesity worsens insulin resistance and increases risk of macrosomia.
4. CLINICAL FEATURES¶
Preeclampsia presents with hypertension, proteinuria, and organ dysfunction (e.g., thrombocytopenia, renal insufficiency). GDM may be asymptomatic but increases risk of macrosomia and cesarean delivery. Infections like cytomegalovirus and herpes can cause congenital anomalies.
4.1 Preeclampsia Symptoms¶
Headache, visual changes, epigastric pain, pulmonary edema, and laboratory abnormalities (thrombocytopenia, elevated liver enzymes). Severe features increase risk of eclampsia (generalized seizures).
4.2 GDM Complications¶
Increased risk of macrosomia (>4000 g), shoulder dystocia, and neonatal hypoglycemia. Maternal risks include preeclampsia and cesarean delivery. Poor glycemic control in early pregnancy increases risk of congenital malformations.
5. DIFFERENTIAL DIAGNOSIS¶
For hypertension: chronic hypertension, renal disease, or endocrine disorders. For diabetes: pregestational diabetes, GDM, or hyperglycemic crises. For infections: cytomegalovirus, rubella, or herpesvirus. Distinguish from normal pregnancy-related changes.
5.1 Hypertension Differentiation¶
Chronic hypertension vs preeclampsia: preexisting vs new-onset BP ≥ 140/90 mmHg. Exclude renal disease or endocrine disorders (e.g., pheochromocytoma).
5.2 Diabetes Differentiation¶
GDM vs pregestational diabetes: OGTT results, family history, and prior diabetes diagnosis. Exclude hyperglycemic crises (e.g., diabetic ketoacidosis).
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis of preeclampsia requires BP ≥ 140/90 mmHg and proteinuria ≥ 300 mg/24h or protein-creatinine ratio ≥ 0.3. GDM is diagnosed via OGTT. Ultrasound and fetal Doppler assess fetal growth and placental function.
Diagnostic Criteria for Preeclampsia¶
| Parameter | Threshold | Notes |
|---|---|---|
| Blood Pressure | ‡140/90 mmHg | Two readings ‡4 hours apart after 20 weeks |
| Proteinuria | ‡300 mg/24h or ‡0.3 protein-creatinine ratio | Exclude chronic hypertension |
| End-Organ Damage | Thrombocytopenia, renal insufficiency, liver impairment | Severe features increase eclampsia risk |
6.1 Preeclampsia Diagnostic Criteria¶
Two BP readings ≥ 140/90 mmHg ≥ 4 hours apart after 20 weeks gestation with proteinuria or end-organ damage. Exclude chronic hypertension or renal disease.
6.2 GDM Diagnostic Criteria¶
Fasting glucose ≥ 95 mg/dL, 1h postload ≥ 180 mg/dL, or 2h postload ≥ 155 mg/dL after 50-g glucose challenge. Confirm with 100-g OGTT.
7. MANAGEMENT & TREATMENT¶
Preeclampsia management includes antihypertensives (labetalol, hydralazine), magnesium sulfate for eclampsia, and delivery for severe features. GDM is managed with dietary therapy, insulin, or metformin. Infections require targeted antimicrobial therapy.
Antihypertensive Therapy in Preeclampsia¶
| Drug | Dose | Notes |
|---|---|---|
| Labetalol | 80–160 mg IV or 100–200 mg PO | Preferred for severe hypertension |
| Hydralazine | 50–100 mg IV or 100–200 mg PO | Effective for acute hypertension |
| Magnesium Sulfate | 4–6 g IV loading, then 1–2 g/h IV | Prevents eclampsia |
7.1 Preeclampsia Treatment¶
Antihypertensives (labetalol, hydralazine) for severe hypertension. Magnesium sulfate for eclampsia. Delivery at 37 weeks for mild preeclampsia; earlier for severe features. Avoid NSAIDs in late pregnancy.
7.2 GDM Management¶
Nutritional therapy with glucose monitoring. Insulin for hyperglycemia. Metformin or glyburide as alternatives. Postpartum screening for diabetes within 4–12 weeks.
8. PROGNOSIS & COMPLICATIONS¶
Preeclampsia increases risk of eclampsia, HELLP syndrome, and maternal mortality. GDM is associated with macrosomia, cesarean delivery, and long-term diabetes risk. Infections like CMV or HSV can cause congenital anomalies or neonatal mortality.
8.1 Preeclampsia Complications¶
Eclampsia (generalized seizures), HELLP syndrome (hemolysis, elevated liver enzymes, low platelets), and maternal mortality. Risk of preterm birth and intrauterine growth restriction.
8.2 GDM Long-Term Risks¶
Increased risk of type 2 diabetes (10% within 5 years), cardiovascular disease, and metabolic syndrome. Neonatal risks include macrosomia and hypoglycemia.
9. SPECIAL CONSIDERATIONS¶
Pregnancy in women with congenital heart disease requires multidisciplinary care. Endocrine disorders (e.g., thyroid disease) require trimester-specific management. Infections like CMV or HSV require antiviral therapy and cesarean delivery for active lesions.
9.1 Congenital Heart Disease¶
Repaired septal defects are low-risk; unrepaired lesions require specialist evaluation. Eisenmenger syndrome is contraindicated for pregnancy; termination may be necessary.
9.2 Thyroid Disease¶
Thyroid-stimulating hormone (TSH) targets vary by trimester. Hyperthyroidism treated with propylthiouracil or methimazole; hypothyroidism managed with levothyroxine.
10. KEY POINTS & CLINICAL PEARLS¶
- Preeclampsia is diagnosed with hypertension and proteinuria after 20 weeks. 2. GDM requires OGTT screening and glucose monitoring. 3. Magnesium sulfate prevents eclampsia. 4. Insulin is preferred for diabetes in pregnancy. 5. Multidisciplinary care is essential for complex pregnancies.