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Abnormalities in a Fetus

Sep 28, 2010 | By Ruth Coleman, M.D.

There are various kinds of abnormalities that can happen to a fetus. Some of them are preventable and some are not. Alcohol and certain drugs can cause abnormalities in various organs that are still developing and can interfere with fetal growth. If a fetus does not receive enough oxygen, this can also interfere with growth. Genetic abnormalities and prematurity cause a variety of problems.

Teratogens

A teratogen is a substance that causes an abnormality in a developing fetus. There are several drugs that are teratogenic, or that cause abnormalities. Some antibiotics can cause ear damage, brain damage, interfere with bone growth or damage the cartilage. Some antiseizure medications cause mental retardation and decreased growth. Approximately 30 to 40 percent of fetuses whose mothers drink more than three ounces of alcohol every day have fetal alcohol syndrome, according to Ellen Elias, M.D., Director of the Special Care Clinic at the Children's Hospital in "Current Diagnosis & Treatment: Pediatrics."

Growth

A fetus can show inadequate growth due to genetics or as the result of various problems. The fetus gets its oxygen from the mother, but may not be getting enough oxygen if there is a problem with the placenta. This can lead to poor growth. Placental problems include abnormalities in the placental blood vessels from diabetes mellitus, kidney disease or hypertension in the mother, as explained by James Kendig, M.D., Professor of Pediatrics at Pennsylvania State University College of Medicine in "The Merck Manual for Healthcare Professionals." The Toxoplasma gondii parasite, rubella virus and cytomegalovirus can also cause decreased growth, as do cigarettes, cocaine and alcohol.

Metabolism

This describes any disorder where a defect in just one gene blocks a metabolic pathway or the steps involved in breaking down a substance. A fetus may have abnormalities in breaking down fatty acids, proteins or carbohydrates. As a result, some substances will accumulate, while there will not be enough of others. This affects various developing organs including the muscles, heart, liver, eyes and brain. The majority of states test for many of these fetal abnormalities, writes Chin-To Fong, M.D., Chief of the Division of Pediatric Genetics at the University of Rochester School of Medicine and Dentistry in "The Merck Manual for Healthcare Professionals."

Chromosomes

This problem can cause abnormalities in a fetus and is even responsible for five to seven percent of fetal deaths, according to F. Gary Cunningham, M.D., Distinguished Chair in Obstetrics and Gynecology at the University of Texas Southwestern Medical Center in "Williams Obstetrics." There can be abnormalities due to the number of chromosomes--either too many or too few. A fetus with Edward's syndrome, Patau's syndrome or Down syndrome is caused by an extra chromosome. A child with with Turner's syndrome has a missing X sex chromosome, while a fetus with Klinefelter's syndrome has an extra X chromosome. In DiGeorge syndrome, a deletion in the chromosome structure causes fetal abnormalities.

Prematurity

In "Williams Obstetrics," Dr. Cunningham explains that there are abnormalities which are a result of a fetus being born prematurely. In respiratory distress syndrome, the cells of the lungs which produce a substance to prevent the lungs from collapsing have not had enough time to make this substance, called surfactant. A fetus may have retinopathy of prematurity, where the retina is damaged because the blood vessels in the retina are not yet mature. Some fetuses may develop hemorrhaging within the brain which can also lead to the formation of cysts.

References

Article reviewed by Billie Jo Jannen Last updated on: Sep 28, 2010

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