Human chromosomes come in 23 pairs, each parent supplying one chromosome in each pair. Trisomy 18 (also called Edwards syndrome) is a genetic condition in which chromosome 18 is a triplet instead of a pair. Like the more commonly known Trisomy 21 (Down syndrome), Trisomy 18 affects all systems of the body and causes distinct facial features.

Trisomy 18 occurs in 1 in 5,000 live births. Unfortunately, most babies with Trisomy 18 die before birth, so the actual incidence of the disorder may be higher. Trisomy 18 affects individuals of all ethnic backgrounds.

Symptoms

Trisomy 18 severely affects all organ systems of the body.

Symptoms may include:

  • Nervous system and brain: Intellectual development disorder and delayed development, increased muscle tone, seizures, and physical malformations such as brain defects
  • Head and face: Small head (microcephaly), small eyes, wide-set eyes, small lower jaw, cleft palate
  • Heart: Congenital heart defects such as ventricular septal defect
  • Bones: Severe growth retardation, clenched hands with 2nd and 5th fingers on top of the others, and other defects of the hands and feet
  • Malformations: Involve the digestive tract, the urinary tract, and the genitals

Cause

Trisomy is caused by a chromosomal problem that affects the egg cells of the mother or the sperm cells of the father. These conditions are present as soon as the baby is conceived, but the parents do not have the condition.

There are some risk factors, including advanced maternal age. But most mothers who are of advanced maternal age have babies with a completely normal chromosomal pattern.

Diagnosis

Screening for certain congenital defects, like Edwards syndrome, involves amniocentesis, which is not a standard screening test. This test is done when a child is at higher-than-average risk of having certain chromosomal abnormalities.

The physical appearance of the child at birth will suggest the diagnosis of Trisomy 18. However, most babies are diagnosed before birth by amniocentesis (genetic testing of the amniotic fluid).

Ultrasound studies of the heart and abdomen can detect specific abnormalities, as can x-rays of the skeleton.

Treatment

Medical care for individuals with Trisomy 18 is supportive and focuses on providing nutrition, treating infections, and managing heart problems.

During the first months of life, infants with Trisomy 18 require skilled medical care. Due to the complex medical problems, including heart defects, and overwhelming infections, most infants have difficulty surviving to age 1 year.

A Word From Verywell

Having a child with a chromosomal defect can be overwhelming for parents, especially if the condition causes severe physical or developmental problems. While you will need to get special medical care for your child, it’s important that you also reach out for professional help and support for yourself as you cope with the emotional and practical issues that you are facing.