Edwards syndrome, also known as trisomy 18, is a genetic disorder caused by the presence of an extra copy of chromosome 18. It is named after John Hilton Edwards, the physician who first described the condition in 1960. Edwards syndrome is a relatively rare condition, occurring in approximately 1 in 5,000 live births.
Diagnosing Edwards syndrome can be challenging, as it involves a combination of prenatal screening tests, diagnostic tests, and clinical evaluation. The goal is to identify any abnormalities or markers that may indicate the presence of trisomy 18.
Prenatal screening tests are typically the first step in diagnosing Edwards syndrome. These tests are non-invasive and aim to assess the risk of chromosomal abnormalities in the fetus. The two most common screening tests are:
If the results of the screening tests indicate a higher risk of Edwards syndrome, further diagnostic tests may be recommended. These tests provide more definitive information about the presence of trisomy 18. The most common diagnostic tests include:
Both amniocentesis and CVS provide highly accurate results, as they directly analyze the fetal chromosomes. However, it's important to note that these tests are invasive and carry a small risk to the pregnancy.
In addition to prenatal screening and diagnostic tests, clinical evaluation is crucial in diagnosing Edwards syndrome. This involves a thorough physical examination of the baby after birth, looking for characteristic features associated with trisomy 18. Some common physical findings in infants with Edwards syndrome include:
It's important to note that not all infants with Edwards syndrome will exhibit all of these features, and some may have additional abnormalities not listed here.
In summary, diagnosing Edwards syndrome involves a combination of prenatal screening tests, diagnostic tests, and clinical evaluation. Prenatal screening tests help assess the risk of chromosomal abnormalities, while diagnostic tests provide more definitive information about the presence of trisomy 18. Clinical evaluation after birth is also crucial in identifying characteristic physical features associated with Edwards syndrome.