Cyclopia is a rare birth defect that occurs when the front part of the brain doesn’t cleave into right and left hemispheres.

The most obvious symptom of cyclopia is a single eye or a partially divided eye. A baby with cyclopia usually has no nose, but a proboscis (a nose-like growth) sometimes develops above the eye while the baby is in gestation.

Cyclopia often results in a miscarriage or stillbirth. Survival after birth is usually a matter of hours only. This condition isn’t compatible with life. It isn’t simply that a baby has one eye. It’s a malformation of the baby’s brain early in the pregnancy.

Cyclopia, also known as alobar holoprosencephaly, occurs in about 1 in 100,000 newborns (including stillbirths). A form of the disease also exists in animals. There’s no way to prevent the condition and there’s currently no cure.

The causes of cyclopia aren’t well understood.

Cyclopia is a type of birth defect known as holoprosencephaly. It means the forebrain of the embryo doesn’t form two equal hemispheres. The forebrain is supposed to contain both cerebral hemispheres, the thalamus and the hypothalamus.

Researchers believe that several factors may raise the risk of cyclopia and other forms of holoprosencephaly. One possible risk factor is gestational diabetes.

In the past, there had been speculation that exposure to chemicals or toxins might be to blame. But there doesn’t appear to be any correlation between a mother’s exposure to dangerous chemicals and a higher risk of cyclopia.

For about one-third of babies with cyclopia or other kind of holoprosencephaly, the cause is identified as an abnormality with their chromosomes. In particular, holoprosencephaly is more common when there are three copies of chromosome 13. However, other chromosome abnormalities have been identified as possible causes, too.

For some babies with cyclopia, the cause is identified as a change with a particular gene. These changes cause the genes and their proteins to act differently, which affects brain formation. In many cases, though, no cause is found.

Cyclopia can sometimes be diagnosed using an ultrasound while the baby is still in the womb. The condition develops between the third and fourth weeks of gestation. An ultrasound of the fetus after this time can often reveal obvious signs of cyclopia or other forms of holoprosencephaly. In addition to a single eye, abnormal formations of the brain and internal organs may be visible with an ultrasound.

When an ultrasound detects an abnormality, but is unable to present a clear image, a doctor may recommend a fetal MRI. An MRI uses a magnetic field and radio waves to create images of organs, a fetus, and other internal features. Both an ultrasound and MRI pose no risk to the mother or child.

If cyclopia isn’t diagnosed in the womb, it can be identified with a visual examination of the baby at birth.

A baby who develops cyclopia often doesn’t survive pregnancy. This is because the brain and other organs don’t develop normally. The brain of a baby with cyclopia can’t sustain all the body’s systems needed to survive.

A live birth of a baby with cyclopia in Jordan was the subject of a case report presented in 2015. The baby died at the hospital five hours after birth. Other studies of live births have found that a newborn with cyclopia usually has only hours to live.

Cyclopia is a sad, but rare occurrence. Researchers believe that if a child develops cyclopia, there might be a greater risk that the parents may carry the genetic trait. This could raise the risk of the condition forming again during a subsequent pregnancy. However, cyclopia is so rare that this is unlikely.

Cyclopia may be an inherited trait. The parents of a baby with the condition should inform immediate family members who may be starting a family about their possible increased risk of cyclopia or other, milder forms of holoprosencephaly.

Genetic testing for parents with a higher risk is recommended. This may not provide sure answers, but conversations with a genetic counselor and a pediatrician about this matter are important.

If you or someone in your family has been touched by cyclopia, understand that it’s not related in any way to the behaviors, choices, or lifestyle of the mother or anyone in the family. It’s likely related to abnormal chromosomes or genes, and developed spontaneously. One day, such abnormalities may be treatable before pregnancy and cyclopia will become preventable.