Version July 2025
INTRODUCTION —
Myasthenia gravis (MG) is a chronic autoimmune neuromuscular disorder characterized by fluctuating weakness and fatigability involving ocular, bulbar, limb, and/or respiratory muscles. MG is characterized by a bimodal distribution of age of onset, with an early peak in the second and third decades (female predominance) and a late peak in the sixth to eighth decades (male predominance). Management typically includes immunotherapy to reduce symptoms and the risk of exacerbations.
This topic will discuss the effect of pregnancy on MG and the management of MG in pregnancy. It will also briefly review clinical and treatment issues related to MG that are discussed in greater detail separately.
●(See "Pathogenesis of myasthenia gravis".)
●(See "Clinical manifestations of myasthenia gravis".)
●(See "Diagnosis of myasthenia gravis".)
●(See "Differential diagnosis of myasthenia gravis".)
●(See "Overview of the treatment of myasthenia gravis".)
EFFECT OF PREGNANCY ON MYASTHENIA GRAVIS —
Pregnancy has a variable effect on the course of MG, and the effects may vary between pregnancies in the same individual [1-14]. Overall, symptoms will remain stable or improve in 50 to 80 percent of pregnancies, while clinical worsening may occur in 20 to 50 percent [13,14]. Acute therapy with intravenous immune globulin or plasma exchange during pregnancy was required in 15 percent in one study [14]. Myasthenic crisis can also occur during pregnancy but is uncommon.
Patients with MG that is under good control before pregnancy can be reassured that they are likely to remain stable throughout pregnancy, although a small proportion may have worsening, particularly in the postpartum period [4]. For patients with active MG before pregnancy, flares are most likely to occur in the first trimester and the postpartum period. Some patients may be diagnosed with MG after developing initial symptoms during pregnancy [5-7].
The first trimester and the acute postpartum period are the times of highest risk for exacerbation [15]. The mortality risk of MG in pregnancy is inversely proportional to the duration of the disease, with the highest risk being within the first year after disease onset [16]. Myasthenic flare may occur after therapeutic abortion secondary to the stress of surgery, but it usually remits following spontaneous abortion [5,8].
PREPREGNANCY PLANNING —
The following general principles apply to the management of patients with MG during pregnancy [4,15,17].
●For patients with MG, pregnancy should be planned well in advance with multidisciplinary management including, where available, maternal-fetal medicine specialists with expertise in managing high-risk, complicated pregnancies. (See "Prenatal care: Initial assessment", section on 'Care provider'.)
●Prepregnancy counseling should include a discussion concerning the safety of therapies for MG, with avoidance or discontinuation of known teratogenic medications (methotrexate and mycophenolate mofetil). (See 'Symptomatic therapy' below.)
●Thymectomy in the year prior to conception is unlikely to result in clinical remission of MG in the mother before pregnancy, and its impact on the risk of neonatal MG is undetermined. Most experts advise young patients to proceed with thymectomy as soon as possible, with the exception of those who are already pregnant. In such cases, thymectomy should be performed when feasible after pregnancy [4].
Retrospective analysis of data from the Medical Birth Registry of Norway found that neonates of mothers with MG who had undergone thymectomy were less likely to develop neonatal MG than those born to mothers without thymectomy (9/72 [13 percent] versus 17/63 [27 percent], relative risk 0.4, 95% CI 0.16-0.94) [18]. These results suggest that thymectomy has a protective effect against neonatal MG. Of note, 25 of the 41 thymectomized mothers had undergone thymectomy an average of five years before the first birth, allowing more time for the benefit of thymectomy to accumulate. However, the strength of this study is limited by the retrospective design, lack of randomization and blinding, and wide confidence intervals.
It is important to note that the beneficial effects of thymectomy are delayed for all patients and may take years to accrue, as discussed separately. (See "Role of thymectomy in patients with myasthenia gravis", section on 'Generalized AChR-positive myasthenia'.)
MANAGEMENT DURING PREGNANCY
General measures — Baseline and surveillance clinical evaluations of pregnant patients with MG include assessment of neurologic status and risks for neurologic deterioration.
●Initial evaluation of the pregnant patient with MG includes assessment of baseline motor strength, respiratory status, and pulmonary function tests. Cardiac status should be followed with electrocardiograms since rare occurrences of focal myocardial necrosis have been recorded in patients with MG [19,20]. Thyroid function tests should be performed since there is an association between MG and other autoimmune diseases [21].
●All infections should be treated promptly. In one study of 65 pregnant individuals with MG, four who had underlying infection (pyelonephritis, endometritis, or mastitis) all developed MG exacerbations [5].
●Complaints of dyspnea or cough call for prompt evaluation of possible myasthenic flare with diaphragm and respiratory muscle weakness [22].
●Physical and emotional stress can exacerbate MG.
Managing medications for myasthenia gravis — Although the normal physiologic changes associated with pregnancy may affect the course of MG, the treatment of MG in pregnancy is similar to that in patients who are not pregnant [4,23]. (See "Overview of the treatment of myasthenia gravis".)
A number of medications may exacerbate weakness in the myasthenic patient and should be avoided whenever possible (table 1).
Symptomatic therapy — Acetylcholinesterase inhibitors such as pyridostigmine are the standard first-line symptomatic treatment for MG, including during pregnancy [4]. Dose adjustment may be required in pregnancy as a result of increased renal clearance, expanded maternal blood volume, delayed gastric emptying, and frequent emesis [22]. Increasing the dose of pyridostigmine should first be accomplished by decreasing the interval of administration, followed by increasing the dose if symptoms persist. (See "Overview of the treatment of myasthenia gravis", section on 'Initial symptomatic therapy'.)
Intravenous acetylcholinesterase inhibitors may produce uterine contractions and should not be used during pregnancy prior to delivery [17]. During labor, however, anticholinesterase medications should be administered parenterally to avoid erratic gastrointestinal absorption. (See 'Labor and delivery' below.)
Immunomodulatory therapy
●Glucocorticoids for most patients – Prednisone is the immunomodulatory agent of choice in pregnancy based on clinical experience of efficacy and risk profile compared with other immunotherapies [4]. However, caution should be exercised when initiating therapy with glucocorticoids since a transient worsening of MG may occur. Glucocorticoids may also produce carbohydrate intolerance, especially during pregnancy. Even though there are no teratogenic effects from glucocorticoids, pregnant patients with MG who rely on these medications should be maintained on the lowest possible dose [2,19]. The use of glucocorticoids to treat MG, including dosing and tapering schedules, is discussed in detail separately. (See "Chronic immunotherapy for myasthenia gravis", section on 'Glucocorticoids'.)
●Alternative or adjunctive immunotherapies – In addition to glucocorticoids, azathioprine and cyclosporine may be used if anticholinesterases fail to control MG exacerbations [4]. These medications have been well studied in pregnancy, mainly in transplant recipients and patients with autoimmune diseases other than MG, and have been found to be relatively safe [24,25]. However, high doses of cyclosporine and azathioprine have been linked to spontaneous abortion, preterm labor, low birth weight, chromosomal damage [2,24,25], and hematologic suppression; they should be reserved for pregnant MG patients who are not well-controlled by or cannot tolerate glucocorticoids, or have significant comorbidities that may worsen with glucocorticoid administration [2,24-26]. The risk of continuing these medications in high doses should be weighed against the benefit of controlling myasthenic symptoms. Mycophenolate mofetil and methotrexate increase the risk of teratogenicity and should not be used in pregnancy [4]. (See "Safety of rheumatic disease medication use during pregnancy and lactation" and "Chronic immunotherapy for myasthenia gravis".)
The data are limited regarding the use of antibody-based biologic therapies during pregnancy for generalized, acetylcholine receptor-positive MG patients [23]. These agents include Fc receptor inhibitors (such as efgartigimod and rozanolixizumab), complement inhibitors (such as ravulizumab and eculizumab), and B-cell depletors (such as rituximab). (See "Chronic immunotherapy for myasthenia gravis", section on 'Eculizumab' and "Chronic immunotherapy for myasthenia gravis", section on 'Ravulizumab' and "Chronic immunotherapy for myasthenia gravis", section on 'Efgartigimod'.)
●Patients with MuSK antibody positive MG – Patients with acetylcholine receptor (AChR)-negative MG who are muscle-specific receptor tyrosine kinase (MuSK) antibody-positive share most of the clinical manifestations of generalized MG but are generally less responsive to acetylcholinesterase inhibitors. For patients with MuSK antibody-associated MG, treatment with prednisone, plasma exchange, or other immunomodulatory therapies may be required [6]. For those with severe and progressive MG, rituximab may be used as a first-line immunomodulatory therapy. However, the data are limited for rituximab use during conception and pregnancy; the risks and benefits must be weighed carefully and discussed with the patient. (See "Safety of rheumatic disease medication use during pregnancy and lactation" and "Chronic immunotherapy for myasthenia gravis".)
●Myasthenic crisis or rescue therapies for severe exacerbations – Plasmapheresis and high-dose intravenous immune globulin are safe in pregnancy [4] and have also been used for myasthenic crisis with variable results [2,5,15,19,27]. These interventions should be reserved for cases where conventional therapy has failed and developing respiratory failure or profound dysphagia and weakness threaten the mother and fetus [11,28]. (See "Myasthenic crisis", section on 'Treat with a rapid-acting immunotherapy'.)
●Deferred thymectomy – Thymectomy is a surgical treatment for selected patients with MG that can improve symptoms and reduce the need for immunotherapy. In pregnant patients with AChR-positive MG and no thymoma, therapeutic thymectomy should be postponed until after pregnancy, since the benefit is unlikely to occur during pregnancy [4]. Thymectomy should be performed in these patients prior to considering a future pregnancy if at all possible. Patients who have undergone thymectomy have fewer exacerbations during or after pregnancy [7].
The management of patients with a thymoma is discussed separately. (See "Treatment of thymoma and thymic carcinoma".)
Medication selection for patients with preeclampsia and eclampsia
●Seizure prevention – While magnesium sulfate is commonly administered for seizure prophylaxis and acute treatment in patients with preeclampsia or eclampsia and preterm labor, it is contraindicated in patients who have MG since it can precipitate a severe myasthenic crisis (table 1) [4,29,30].
For treatment of seizures in eclampsia, we use a benzodiazepine (eg, lorazepam or diazepam) plus an antiseizure medication (eg, phenytoin or levetiracetam) in agreement with society guidelines [31,32]. The administration of antiseizure medications in eclampsia is discussed in detail separately. (See "Eclampsia", section on 'Antiseizure medication'.)
For the prevention of seizures in patients with preeclampsia, we use an antiseizure medication (eg, phenytoin or levetiracetam). The indications for and administration of antiseizure medications in preeclampsia are discussed in detail separately. (See "Preeclampsia: Intrapartum and postpartum management and long-term prognosis", section on 'Seizure prophylaxis'.)
●Hypertension management – Severe hypertension in patients with MG can be treated with intravenous hydralazine or oral nifedipine, while beta-blockers should be avoided if possible (table 1) [32].
Fetal assessment — The development of fetal abnormalities related to the transplacental passage of IgG AChR-Abs is a major concern during pregnancy. (See "Neuromuscular junction disorders in newborns and infants", section on 'Neonatal myasthenia gravis'.)
●Methods – The perception of fetal movement may be altered in patients with MG. Assessment of fetal well-being may include the nonstress test or biophysical profile. Methods of fetal assessment are discussed in detail separately. (See "Fetal assessment: Overview of antepartum tests of fetal well-being", section on 'Fetal assessment techniques' and "Nonstress test and contraction stress test".)
Continuous fetal monitoring is indicated during a myasthenic crisis if the fetus is at a viable gestational age (eg, at least 23 menstrual weeks of gestation) given the high risk of maternal and fetal hypoxia.
●Findings – Abnormal sonographic findings in affected pregnancies may include polyhydramnios due to impaired fetal swallowing [33,34]. Decreased fetal movement and breathing have also been described [33].
Fetal arthrogryposis multiplex congenita is the most severe finding in the fetus with neonatal MG; lack of generalized fetal movement and diaphragmatic excursion may rarely produce joint contractures and pulmonary hypoplasia [33,35]. Several studies describe a direct relationship between high maternal titers of AChR-Abs and fetal arthrogryposis multiplex congenital [33,35]. Whereas ultrasound may be able to detect these abnormalities during the antepartum period, its utility for predicting clinical outcomes is not well defined.
LABOR AND DELIVERY
Mode of delivery — Spontaneous vaginal delivery is the objective and should be encouraged [4]. Cesarean delivery should be reserved for the usual obstetrical indications. Appropriate steps should be taken to circumvent the effects of maternal fatigue on delivery since stress and exertion can precipitate a myasthenic crisis [21]. The first stage of labor is not affected by MG because the uterus is composed of smooth muscle and lacks the postsynaptic acetylcholine receptor. In contrast, the second stage of labor may be affected because the voluntary striated muscles used during expulsive efforts may easily weaken. Excessive maternal fatigue may result. Operative vaginal delivery may reduce maternal fatigue and weakness. In a systematic review that included 824 pregnancies, spontaneous vaginal delivery was performed for 56 percent of births, operative vaginal delivery for 10 percent, cesarean birth for obstetric indications in 30 percent, and cesarean birth for MG only 3 percent of deliveries [36].
Monitoring and management of neuromuscular status
●Anesthesiology consultation – Consultation with an anesthesiologist before labor is recommended, since patients with MG who undergo general anesthesia may be at increased risk for requiring mechanical ventilation [37,38]. The selection of anesthetic techniques is dependent on several factors. Regional anesthesia is recommended for mild to moderate disease when vaginal delivery is anticipated, allowing for adequate anesthesia if vacuum or forceps are needed; it also can reduce fatigue associated with the second stage of labor. General endotracheal anesthesia is recommended for patients with severe disease and compromised respiratory or bulbar status [19].
●Medications – Neuromuscular blocking agents should be avoided if neuromuscular monitoring and sugammadex are unavailable since patients with MG have altered acetylcholinesterase activity. Due to the relative resistance to succinylcholine, larger doses are often required leading to a prolonged block [19]. Patients with MG are more sensitive to inhaled anesthetics including sevoflurane, desflurane, halothane, and isoflurane [19,39].
Sedatives, opioids, and tranquilizers can potentiate respiratory depression in this population and should be administered judiciously. When using opioids or other sedatives for pain control, pulse oximetry and frequent assessment of respiratory rate are recommended. Nonsteroidal anti-inflammatory drugs such as ketorolac tromethamine may also be used for postpartum or postoperative pain.
During labor, anticholinesterase medications should be administered parenterally to avoid erratic gastrointestinal absorption. The dose of pyridostigmine is individualized based on patient symptoms. The parenteral dose of pyridostigmine is equivalent to one-thirtieth of the patient's oral dose.
The periprocedural anesthetic management of patients with MG is discussed in greater detail separately. (See "Anesthesia for the patient with myasthenia gravis or Lambert-Eton myasthenic syndrome", section on 'Anesthesia management'.)
●Respiratory status – The maternal respiratory status (respiratory rate, pulse oximetry) should be monitored carefully because stress and fatigue associated with labor and delivery may precipitate the worsening of symptoms. Another issue is that chronic glucocorticoid therapy can suppress the hypothalamic-pituitary-adrenal axis and lead to adrenal insufficiency during times of stress such as labor and delivery. Therefore, some experts suggest that patients on long-term glucocorticoids who take prednisone or equivalent at a dose >7.5 mg/day should receive stress-dose hydrocortisone during the intrapartum period [17]. Other experts use somewhat different thresholds to determine the need for glucocorticoid coverage based upon the patient's history of glucocorticoid intake and the likelihood of hypothalamic-pituitary-adrenal axis suppression, as discussed elsewhere. (See "The management of the surgical patient taking glucocorticoids".)
Complications — Pregnant patients with MG have an increased incidence of preterm labor and birth in some studies [40,41], although this is not confirmed by other studies [8]. In one review, the rates of preterm birth occurring prior to 37 and 34 weeks gestation were 12 and 4 percent, respectively [36].
Estimates of perinatal mortality rates for infants born to patients with MG vary widely [1,40]. In a retrospective population study, perinatal mortality was not significantly higher among 127 births by Norwegian females with MG compared with those of a reference group without MG (2.4 versus 1.4 percent) [40]. However, females with MG had a significantly higher risk of delivery complications than the reference group (41 versus 33 percent); the most common complication was premature rupture of membranes. Cesarean deliveries were also performed more frequently in females with MG (17 versus 9 percent of deliveries); half were elective. In contrast, a population-based study from Taiwan found no significant differences between pregnant patients with MG and controls for the risk of delivery complicated by low birth weight, small for gestational age, or cesarean delivery [42].
An earlier study found that the death rate due to fetal anomalies was higher in the myasthenic population compared with the normal population (18 versus 2.2 per 1000 live births) [1].
POSTPARTUM MANAGEMENT
Monitoring for neonatal MG — All infants of mothers with MG should be observed and monitored in a special care nursery for the first 48 to 72 hours of life for any evidence of weakness caused by transient neonatal MG [15]. Symptoms of respiratory distress, poor feeding, and flaccid tone can appear within hours after birth and may persist for up to three months.
Transient neonatal MG develops in 10 to 20 percent of infants born to mothers with MG due to transplacental passage of IgG anti-acetylcholine receptor antibodies (AChR-Ab) [43]. Though definitive data are lacking, a small retrospective study found no correlation between neonatal MG and the maternal IgG anti-AChR titer [44]. In addition, a small prospective study found that the duration of maternal disease and medication usage for MG were not associated with the occurrence of neonatal MG [45].
Among mothers with a child affected by transient neonatal MG, the risk of recurrence with subsequent pregnancies is approximately 75 percent. (See "Neuromuscular junction disorders in newborns and infants", section on 'Neonatal myasthenia gravis'.)
Breastfeeding — Glucocorticoids can be used safely in lactation. Anticholinesterase drugs are found in breast milk at low levels and are therefore considered safe in lactation unless high doses are required [2]. Breastfeeding may continue along with the use of azathioprine, cyclosporine, tacrolimus, IVIG, or plasma exchange. Breastfeeding is not recommended for patients with MG taking mycophenolate or methotrexate [15,46].
SOCIETY GUIDELINE LINKS —
Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Myasthenia gravis" and "Society guideline links: Thymomas and thymic carcinomas".)
INFORMATION FOR PATIENTS —
UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Myasthenia gravis (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Effect of pregnancy on MG – Myasthenia gravis (MG) is an autoimmune disorder characterized by weakness and fatigability of skeletal muscles due to dysfunction of the neuromuscular junction. Pregnancy has a variable effect on the course of MG. The first trimester and the acute postpartum period are the times of highest risk for exacerbation. (See 'Effect of pregnancy on myasthenia gravis' above.)
●Prepregnancy planning – For patients with MG, pregnancy should be planned well in advance with multidisciplinary communication among specialists to optimize the clinical management of MG and to minimize risks to the fetus. (See 'Prepregnancy planning' above.)
●Treatment during pregnancy
•MG treatment – Anticholinesterase agents such as pyridostigmine are the standard first-line symptomatic treatment for MG. Dose adjustment may be required in pregnancy. Prednisone is the immunomodulatory agent of choice in pregnancy. (See 'Managing medications for myasthenia gravis' above.)
The use of other immunomodulatory agents for patients unresponsive to first-line options should be individualized based on the assessment of overall risks and benefits. These agents include azathioprine, tacrolimus, and cyclosporine. Mycophenolate mofetil and methotrexate increase the risk of teratogenicity and should not be used in pregnancy.
•Contraindications and use of specific medications – Magnesium sulfate is contraindicated in patients who have MG, since it can precipitate a severe myasthenic crisis (table 1). Beta-blockers and nondepolarizing muscle relaxants should be avoided. (See 'Managing medications for myasthenia gravis' above.)
For the management of preeclampsia or eclampsia in patients with MG, an antiseizure medication such as levetiracetam can be used for seizure prevention, and a benzodiazepine plus an antiseizure medication can be used for acute seizure treatment. Severe hypertension can be treated with methyldopa or hydralazine. (See 'Medication selection for patients with preeclampsia and eclampsia' above.)
•Management during labor – The second stage of labor may be affected in patients with MG because the voluntary striated muscles used during expulsive efforts may easily weaken. Appropriate steps should be taken to circumvent the effects of maternal fatigue on delivery since stress and exertion can precipitate a myasthenic crisis. During labor, anticholinesterase medications should be administered parenterally to avoid erratic gastrointestinal absorption. (See 'Labor and delivery' above.)
●Postpartum management
•Monitoring for neonatal MG – All infants of mothers with MG should be observed in a special care nursery for the first 48 to 72 hours of life, as transient neonatal MG develops in 10 to 20 percent of infants born to mothers with MG. (See "Neuromuscular junction disorders in newborns and infants", section on 'Neonatal myasthenia gravis'.)
•Breastfeeding – Glucocorticoids can be used safely in lactation. Anticholinesterase drugs are found in breast milk at low levels and are therefore considered safe in lactation unless high doses are required. Mycophenolate, methotrexate, and some other immunotherapeutic agents can cause immunosuppression in the infant and are therefore contraindicated in breastfeeding mothers. (See 'Breastfeeding' above.)
