Individuals with myotonic dystrophy may have concerns about starting a family because of the risks of passing the disease to their children. Discussing family planning issues with a genetic counselor can help individuals make an informed decision.

Multiple diagnostic options exists for patients who are considering having children. These include:

• Preimplantation genetic diagnosis (also known as PGD). This is the diagnosis of a genetic condition before pregnancy. This form of testing is done on a woman's eggs using in vitro fertilization. Unfertilized eggs are taken from the woman by a doctor and are fertilized outside the womb in a laboratory. The embryos are tested for DM at the 6 to 8 cell stage. Only non DM-affected fertilized eggs are implanted into the uterus.
• Prenatal diagnosis. Parents wishing to find out during pregnancy whether their fetus has inherited the myotonic dystrophy gene can undergo prenatal testing. Two types of tests are available:
• Amniocentesis. This procedure involves removing a smaple of fluid from the womb that contains skin cells shed by the fetus. The cells are then grown in the lab to provide DNA for testing. The test is typically done 15 weeks into the pregnancy and can take 2-3 weeks for results to become available.
• Chorionic villus sampling (CVS). The doctor removes a piece of tissue from the edge of the placenta using a needle inserted through the abdomen or vagina. The sampled tissue contains the same genetic information as the fetus; the DNA is isolated and tested for the presence of the myotonic dystrophy mutation. The test can be done in the first trimester (generally around 10 weeks into the pregnancy) and results are typically available within 1-2 weeks.

Mothers who have DM1 should be closely monitored during pregnancy because they have a higher risk of having a child with congenital DM1. In these cases, excessive amniotic fluid (hydramnios) can accumulate, which can usually be seen during ultrasound examination. Decreased fetal movement is frequently noted. Also, breech presentation and weak uterine contractions can cause long or difficult deliveries, often resulting in Caesarean births.

Newborns with congenital myotonic dystrophy require immediate intensive medical support. Delivery at a medical center with high-risk neonatal support may be recommended. Regardless of whether or not testing is done, individuals with family history or symptoms of myotonic dystrophy should inform their obstetrician so the medical team can prepare for the possible complications seen with these children.

Clinical Recommendations for People of Pregnancy Potential with Myotonic Dystrophy

• Clinical Recommendations for People of Pregnancy Potential with Myotonic Dystrophy: This resource is designed to provide clinicians with an overview of risks and care recommendations for individuals living with myotonic dystrophy (DM) who are pregnant or considering pregnancy. Because DM is a highly variable and multi-systemic disease, it is important to conduct individual risk assessments on a case-by-case basis. Additionally, due to the myriad manifestations and severities of DM, this document describes a variety of outcomes that may or may not be applicable to a patient.
• Spanish - Recomendaciones clínicas para personas con distrofia miotónica en edad fértil