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Autoimmune Disorders in Pregnancy
Autoimmune disorders are 5 times more common among women, and incidence tends to peak during reproductive years. Thus, these disorders commonly occur in pregnant women.
Antiphospholipid syndrome (APS—see Antiphospholipid Antibody Syndrome (APS)) is an autoimmune disorder that predisposes patients to thrombosis and, during pregnancy, increases risk of fetal demise, pregnancy-induced hypertension, preeclampsia, and intrauterine growth restriction.
APS is caused by autoantibodies to certain phospholipid-binding proteins that would otherwise protect against excessive coagulation activation.
APS is suspected in women with a history of one fetal loss or ≥ 3 embryonic losses, prior unexplained venous thromboembolism, or new venous thromboembolism during pregnancy.
Diagnosis is made by measuring levels of circulating antiphospholipid antibodies with positive results on ≥ 2 occasions 12 wk apart.
Immune thrombocytopenia (ITP—see Immune Thrombocytopenia (ITP)), mediated by maternal antiplatelet IgG, tends to worsen during pregnancy and increases risk of maternal morbidity.
Corticosteroids reduce IgG levels and cause remission in most women, but improvement is sustained in only 50%. Immunosuppressive therapy and plasma exchange further reduce IgG, increasing platelet counts. Rarely, splenectomy is required for refractory cases; it is best done during the 2nd trimester, when it causes sustained remission in about 80%. IV immune globulin increases platelet count significantly but briefly, so that labor can be induced in women with low platelet counts. Platelet transfusions are indicated only when cesarean delivery is required and maternal platelet counts are < 50,000/μL.
Although antiplatelet IgG can cross the placenta, it only very rarely causes fetal or neonatal thrombocytopenia. Maternal antiplatelet antibody levels (measured by direct or indirect assay) cannot predict fetal involvement. Risk of neonatal intracranial hemorrhage due to maternal ITP is not affected by the mode of delivery nor by birth trauma. Accordingly, the current accepted practice is vaginal delivery, without routinely determining the fetal platelet count, and cesarean delivery only for obstetric indications.
Myasthenia gravis (see Myasthenia Gravis) varies in its course during pregnancy. Frequent acute myasthenic episodes may require increasing doses of anticholinesterase drugs (eg, neostigmine), which may cause symptoms of cholinergic excess (eg, abdominal pain, diarrhea, vomiting, increasing weakness); atropine may then be required. Sometimes myasthenia becomes refractory to standard therapy and requires corticosteroids or immunosuppressants.
During labor, women may need assisted ventilation and are extremely sensitive to drugs that depress respiration (eg, sedatives, opioids, Mg sulfate). Because the IgG responsible for myasthenia crosses the placenta, transient myasthenia occurs in 20% of neonates, even more if mothers have not had a thymectomy.
RA (see Rheumatoid Arthritis (RA)) may begin during pregnancy or, even more often, during the postpartum period. Preexisting RA generally abates temporarily during pregnancy. The fetus is not specifically affected, but delivery may be difficult if the woman’s hip joints or lumbar spine is affected.
If a woman develops an RA flare during pregnancy, first-line treatment usually begins with prednisone. For refractory cases, other immunosuppressants may be required.
SLE (see Systemic Lupus Erythematosus (SLE)) may first appear during pregnancy; women who have had an unexplained 2nd-trimester stillbirth, a fetus with growth restriction, preterm delivery, or recurrent spontaneous abortions are often later diagnosed with SLE.
The course of preexisting SLE during pregnancy cannot be predicted, but SLE may worsen, particularly immediately postpartum. Outcomes are better if conception can be delayed until the disorder has been inactive for at least 6 mo, the drug regimen has been adjusted in advance, and hypertension and renal function are normal.
Complications may include
Significant preexisting renal or cardiac complications increase risk of maternal morbidity and mortality. Diffuse nephritis, hypertension, or the presence of circulating antiphospholipid antibodies (usually anticardiolipin antibody or lupus anticoagulant) increases risk of perinatal mortality. Neonates may have anemia, thrombocytopenia, or leukopenia; these disorders tend to resolve during the first weeks after birth when maternal antibodies disappear.
If hydroxychloroquine was used before conception, it may be continued throughout pregnancy. SLE flares are usually treated with low-dose prednisone, IV pulse methylprednisolone, hydroxychloroquine, and/or azathioprine. High-dose prednisone and cyclophosphamide increase obstetric risks and are thus reserved for severe lupus complications.
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