What is myasthenia gravis?

Myasthenia gravis is a complex autoimmune disorder. It causes antibodies to destroy the connections between your muscles and nerves. This causes muscle weakness and tiredness.

Only about 20 out of 100,000 people get this disorder. In young people, myasthenia gravis happens more in women than in men. Some people just have weakness in the eye muscles. Others have weakness in the face, arms, and legs.

Myasthenia gravis may be of special concern during pregnancy. Some women with the disease have breathing problems (myasthenic crisis) while pregnant. In other women, the disease may go into remission. This is when some or all symptoms go away. Pregnancy doesn't seem to make the disease worse.

What causes myasthenia gravis?

Myasthenia gravis is an autoimmune disorder. This means the body makes antibodies that attack its own tissues. People get myasthenia gravis when their body’s immune system attacks the connections of the nerves and muscle cells. It isn't clear why people get autoimmune disorders. It’s likely a mix of your genes, things in the environment, and allergies.

What are the symptoms of myasthenia gravis?

The main symptom of myasthenia gravis is weak muscles. Muscles get weaker with activity and better with rest. Affected muscles are often in the eyes, face, jaw, neck, arms and legs, and muscles used to breathe. People also get very tired. Pregnant women with myasthenia gravis often have more weakness and are more tired. This is because of the added weight and effort of pregnancy. Some women who get very weak and tired may have a myasthenic crisis. Their breathing muscles can’t work normally, and they have respiratory failure. The main symptom of myasthenic crisis is more problems with breathing. You may be more likely to have a myasthenic crisis when you are in labor.

How is myasthenia gravis diagnosed?

The diagnosis of myasthenia gravis starts with a review of your health history and a physical exam, including an exam of the nervous system. Your healthcare provider will diagnose myasthenia gravis by testing for muscle strength and how well nerves work.

Tests include:

• Tests for certain antibodies

• Nerve conduction tests 

• Electromyography to test the connections between nerves and muscles

You may need other tests to rule out other conditions with similar symptoms.

How is myasthenia gravis treated?

Treatment depends on how bad the disease is. It may include steroids and medicines that suppress the immune system.

You'll need close watching if you're pregnant and have myasthenia gravis. You may need to see your healthcare provider more often.

You may need to:

• Change the type of medicine you take and the amount you take

• Stay away from emotional and physical stress

• Check for signs of myasthenic crisis

You may also have:

• Ultrasound. This imaging test uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Your healthcare provider uses ultrasound to look at organs and the blood flow through blood vessels, and to watch the growth of your developing baby.

• Fetal monitoring. This is done to look for signs of muscle weakness that may show that the baby has myasthenia gravis.

• Other fetal testing. This includes using Doppler flow studies to watch blood flow in the uterus and umbilical cord. Your provider will also watch for signs of preeclampsia and fetal growth problems.

You can increase your chances of having a healthy pregnancy by getting early prenatal care and working with your healthcare providers to manage your disease.

What are possible complications of myasthenia gravis?

Myasthenic crisis and respiratory failure are the major complications of myasthenia gravis, even when you're not pregnant.

But when you're pregnant, there are other concerns. These complications of pregnancy may be more likely when you have myasthenia gravis:

• Preterm labor. This is labor before 37 weeks of pregnancy. It may be because of certain medicines used to treat myasthenia gravis.

• Difficult delivery. Myasthenia gravis doesn't affect the muscles of the uterus. But the muscles needed for pushing can be affected. This may make forceps and vacuum-assisted deliveries more likely.

• Baby born with myasthenia gravis. Approximately 10% to 15% of babies born to women with myasthenia gravis may have the infant form of the disorder (neonatal myasthenia gravis). It happens when antibodies common in myasthenia gravis cross the placenta to the baby. These babies may be weak, with poor suck, and they may have breathing problems. This condition is often short-term (temporary), lasting only a few weeks.

Women with myasthenia gravis shouldn't use the medicine magnesium sulfate. This medicine is commonly used to treat high blood pressure and preterm labor. This medicine blocks the nerve-muscle connections and can make muscle weakness worse.

When should I call my healthcare provider?

Call your healthcare provider if you have a change in your regular symptoms or if your weakness and tiredness get worse. If you start to have breathing problems, it could be the beginning of a myasthenic crisis. Get medical help right away.

Key points about myasthenia gravis

• Myasthenia gravis is a complex autoimmune disorder. It causes antibodies to destroy the connections between your muscles and nerves. This causes muscle weakness and tiredness.

• This condition may be of special concern during pregnancy. It can make complications more likely.

• If you have myasthenia gravis when you're pregnant, you'll need to be closely watched.

• You can raise your chances for a healthy pregnancy by getting early prenatal care and working with your healthcare providers to manage your disease.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down questions you want answered.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions, especially after office hours or on weekends.