Autoimmune diseases and pregnancy: Myasthenia Gravis

The immune system is a complex mechanism of protection in which specialized cells detect invaders and recognize foreign elements in the body, and attack them. Pregnancy is an exceptional situation in which two organisms live together, with two separated immune systems, the mother's and the embryo's one, and the body should step aside to allow the birth of the new life. In autoimmune diseases, the body recognizes as an invader some cellular structures of the body itself, and reacts against it, causing local or general complications.

Myasthenia Gravis is an autoimmune disease that affects neuromuscular junctions of voluntary contraction muscles: the skeletal muscle's contraction is controlled by some chemical substances called neurotransmitters, that fly through the space existing between the end of a neuron and its receptor - in this case, in a muscle. One of these neurotransmitters is called acetylcholine and, in a healthy person, acetylcholinesterase is the enzyme which removes the excess of acetylcholine from the synaptic space (the space through which neurotransmitters fly to the receptor).

In Myasthenia there are antibodies which recognize acetylcholine's receptors and avoid the transmission to be done in a correct way, causing muscle fatigue and muscle fluctuating weakness, among other effects.

Some of the symptoms of this illness are double vision, drooping eyelid, complications talking, fatigue... and more actions in which voluntary contractions are involved. The most complicated aspect in case of pregnancy is the difficulty breathing due to the weakness of the rib cage's muscles.

Through a treatment of acetylcholinesterase inhibitors, it is possible to have a normal life, and the pregnancy can be carried out under the strict supervision of the specialist.

Pregnancy with Myasthenia

There's no way to predict Myasthenia's evolution during the pregnancy: they have registered cases of pregnant women in which Myasthenia had increased, while in others it had remained at the same level than before the pregnancy, and sometimes it had decreased. Even when Myasthenia doesn't turn more serious, more fatigue and weakness have been noticed, due to the increasing weight of the pregnancy.

Medication with acetylcholinesterase inhibitors can't trespass placenta, and it can be maintained during the pregnancy; the use of immunosuppressive prednisone is also permitted, still immunosuppressives in general are controversial, due to their mutagenic effects. According to the studies, the dose of acetylcholinesterase inhibitor shouldn't vary during the pregnancy - this will only depend on the severity of the condition.

Women with Myasthenia who become pregnant should turn to a gynecologist, who will observe the evolution of the disease during the pregnancy. They suggest to increase the resting hours, in order to reduce the intensity of Myasthenia's effects, and to be careful in case of possible increments of the symptoms.

Prenatal, labour y perinatal complications due to Myasthenia

The muscle layer of the uterus, called myometrium, is constituted of a smooth muscle, so that Myasthenia does not affect its function. The labour is the moment in which Myasthenia can make the difference: the first part, the dilation, happens faster than in a healthy person, but the second part, the expulsion, where the abdomen's muscles are crucial, there can be complications in pushing, and forceps may be necessary to help the birth.

Cesarean only is indicated when absolutely necessary, and anesthesia should be limited as much as possible to local anesthesia, in order to avoid muscle relaxants.

Neonatal Myasthenia Gravis

Myasthenia doesn't affect the correct fetal development during the pregnancy.

10-20% of children born to mothers with Myasthenia have a transitional situation of general weakness during the first days of weeks, due to the mother's antibodies that have passed through the placenta, and typical signals of this can be a weak crying and a reduction in the sucking reflex. We are talking about small quantities of acetylcholinesterase inhibitors, which won't complicate the development of the newborn.

Breastfeeding is not recommended if the antibodies' concentration in blood (called antibodies avidity) is high, otherwise important doses of cholinesterase inhibitors will be necessary.

In conclusion, pregnancy with Myasthenia Gravis is possible, although it requires a strict follow-up of the pregnancy's development, to verify that the drug is adapted to the mother's necessities at any time, and, in case it appears in the newborn, to diagnose it and successfully treat it.