Chapter 60. Comorbid Diseases in Pregnancy

Many medical conditions can present in the context of pregnancy, either as a preexisting condition or arising during pregnancy. This chapter will focus on conditions that require different management when encountered in the pregnant patient. Some disorders are covered in other chapters within this text, including hypertension (Chapters 26 and 61), HIV infection (Chapter 62), and cardiac rhythm disturbances (Chapter 2). Of note, when managing any acute complication of pregnancy, supplemental oxygen therapy and left lateral decubitus positioning are recommended to optimize oxygen delivery to the fetus.

Diabetics are at increased risk for complications of pregnancy and acute complications of diabetes. Many patients with gestational diabetes (GD) are managed with diet alone, with a few requiring oral hypoglycemics (metformin or glyburide). Insulin therapy is necessary for some patients with GD and nearly all patients with Type I or II diabetes. Insulin requirements increase as a pregnancy progresses, from 0.7 to 1.0 units/kg/d at term.

Pregnant patients are at increased risk of diabetic ketoacidosis (DKA), especially those who are noncomplaint, have hyperemesis, or are on sympathomimetic agents for tocolysis. Treatment of DKA is the same for pregnant and nonpregnant patients: isotonic fluid resuscitation to correct volume deficits, administration of continuous insulin, correction of electrolyte abnormalities (potassium and magnesium,) and treatment of the underlying cause (see Chapter 129).

Mild hypoglycemia is treated with a snack of milk and crackers, with care to avoid subsequent hyperglycemia. IV dextrose and/or IM glucagon is used in the obtunded patient, followed by an IV 5% dextrose solution at 50 to 100 mL/h.

Hyperthyroidism in pregnancy increases the risk of preeclampsia, congenital anomalies, and neonatal morbidity. Clinical features may be subtle and may include hyperemesis gravidarum. Hyperthyroidism in pregnancy is treated with propylthiouracil (PTU), started at 50 milligrams PO 3 times daily (may be increased to 200 milligrams 3 times daily). Patients on PTU are at risk for purpuric rash and agranulocytosis. The use of radioactive iodine is contraindicated in pregnancy. Thyroid storm presents with fever, volume depletion, and cardiac decompensation. Management is similar to nonpregnant patients and includes PTU, sodium iodide, propranolol, cooling measures, and supportive care (see Chapter 131).

Dysrhythmias may be precipitated by pregnancy. Supraventricuar tachycardias are treated with β-blockers, adenosine, verapamil, diltiazem, and digoxin at usual dosages. Patients with atrial fibrillation who require anti-coagulation should be managed with unfractionated or low molecular weight heparin (LMWH). Electrical cardioversion may be used to treat tachyarrthymias when indicated and have not been shown to be harmful to the fetus. Amiodarone should only be used to treat resistant, life-threatening dysrhythmias.

Factors associated with increased risk of thromboembolism include advanced maternal age, increasing parity, multiple gestations, operative delivery, bedrest, and obesity. Symptoms of deep venous thrombosis (DVT) and pulmonary embolism (PE) may be mistaken for symptoms of normal pregnancy. Diagnosis of DVT is usually made by compression ultrasonography. CT angiography may be used to diagnose PE, and exposes the fetus to less radiation than ventilation-perfusion scan. MRI may also be used, but is less well studied in pregnancy. The utility of d-dimer testing in pregnancy is controversial. (See Fig. 60-1 for a suggested diagnostic algorithm.) DVT and PE are treated with unfractionated or low molecular weight heparin at usual doses. Warfarin is contraindicated (see Chapter 25).

The presentation and management of acute asthma are similar in pregnant and nonpregnant patients. Acute therapy includes maintenance of oxygen saturation above 95%, administration of inhaled β2-agonists, and early administration of systemic corticosteroids. Aerosolized ipratropium may be added in severely obstructed patients. Terbutaline sulfate, 0.25 milligram SC every 20 min, may also be used. Subcutaneous epinephrine should be avoided, if possible. Continuous fetal monitoring should be performed after 20 weeks' gestation. Criteria for intubation or admission are similar in pregnant and nonpregnant patients; standard agents for rapid sequence intubation are used.

Urinary tract infection is the most common bacterial infection in pregnancy. Clinical features are similar in pregnant and nonpregnant women. Simple cystitis may be treated for 7 to 10 days with nitrofurantoin sustained release 100 milligrams PO twice daily, amoxicillin 500 PO 3 times daily, or cephalexin 500 milligrams PO 4 times daily. Pregnant patients with pyelonephritis are treated aggressively because of increased risk of preterm labor and sepsis, and should be admitted for IV hydration and antibiotics (cefazolin 1 to 2 grams IV, or ampicillin 1 gram IV plus gentamicin 1 milligram/kilogram IV). Many providers continue antibiotic suppression for the remainder of the pregnancy. Quinolones are contraindicated in pregnancy. Avoid sulfonamides during the third trimester.

Women with sickle cell disease are at higher risk for miscarriage, preterm labor, and vaso-occlusive crises. Clinical features, evaluation, and treatment are similar to nonpregnant patients. Management of vaso-occlusive crisis includes aggressive hydration, analgesia, and fetal monitoring (if the fetus is viable). Opiates can be used; NSAIDs should be avoided, particularly after 32 weeks' gestation. Blood transfusion should be considered when conservative measures have failed, or with severe anemia, preeclampsia, hypoxemia, acute chest syndrome, or a new-onset neurological event. Hydroxyurea should be discontinued in pregnancy.

Headaches can be a presenting symptom of a wide variety of benign and life-threatening disorders, including intracranial hemorrhage, mass, infection, and preeclampsia/eclampsia. Warning symptoms of potentially life-threatening disease include acute onset, postpartum headaches (increased risk of thrombosis), neurological deficits, and papilledema or retinal hemorrhages. If indicated, CT scan of the brain should be performed with appropriate shielding of the uterus. Migraine headaches should be treated with acetaminophen, narcotics, and antiemetics. Ergot alkaloids and triptans should not be used.

Seizure frequency may increase in patients with epilepsy due to altered drug pharmacokinetics. Acute seizure management is similar to that in nonpregnant patients (see Chapter 146). Status epilepticus with prolonged maternal hypoxia and acidosis has a high mortality rate for the mother and infant, and should be treated aggressively with early intubation and ventilation. Chronic seizure control is best managed by the patient's physician. Valproic acid, carbamazepine, lamotrigine, and phenytoin should be avoided due to teratogenicity.

Cocaine use is associated with increased incidence of fetal death in utero, placental abruption, preterm labor, premature rupture of membranes, spontaneous abortion, intrauterine growth restriction, and fetal cerebral infarcts. Treatment of acute cocaine intoxication is unchanged in pregnancy. Opiate withdrawal in pregnant women is treated with methadone or buprenorphine in conjunction with an obstetrician and drug addiction specialist. Clonidine may be used acutely to blunt symptoms. Alcohol use contributes to increased rates of spontaneous abortion, low birthweight, preterm deliveries, and fetal alcohol syndrome. Benzodiazepines, a category D class, are best avoided in early pregnancy, but can be used in the context of severe alcohol withdrawal or severe cocaine intoxication.

Table 60-1 provides general recommendations regarding drug use in pregnancy. For any drug not listed in the table, check the manufacturer's recommendations before administration and check your hospital formulary or drug databases for the most current information.

Between 4% to 20% of pregnant women are victims of intimate partner violence. They are at risk for placental abruption, uterine rupture, preterm labor, and fetal fractures. Injured pregnant women should be treated according to usual trauma protocols. Rh immunoglobulin, 300 micrograms intramuscularly, should be considered after blunt abdominal trauma in Rh-negative patients.

The threshold for teratogenesis from ionizing radiation is 10 rads, with the first trimester being the most vulnerable period. The effects of radiation exposure change with gestational age. The second to the eighth week post conception is the period of organogenesis, when the fetus is most at risk for birth defects. Mental retardation and other problems may occur with significant x-ray exposure between 8 and 25 weeks. No single test exceeds the teratogenic threshold, but the effects are cumulative, and multiple tests may exceed the threshold. Ultrasound and magnetic resonance imaging have not been associated with teratogenic effects.