It is not uncommon for early ultrasound tests to show two fetuses, but at a later viewing (or at birth) only one baby shows up. This was first described in 1945, and has since found to be quite common.

This isn't a problem with the ultrasound - one of the fetuses is actually disappearing. This may be caused by the reabsorption of one fetus, the formation of a papyraceous (it's still there, but it's "mummified" or compressed), or development of a small abnormality on the placenta, such as a cyst, subchorionic fibrin, or amorphous material.

If this happens during the first trimester, there probably won't be any damage to the other fetus or the mother. If it happens any later, the remaining fetus might be at risk for cerebral palsy, or cutis aplasia. The mother may have complications in labor or an infection from the dead fetus. This could result in death. Women over 30 years of age are more likely to have a vanishing fetus.

There aren't any certain figures, but a vanishing twin probably makes it's appearance/exit in about 1/5 to 1/3 of the cases multifetal gestation.

Boy Gives Birth To His Twin

Kazakhstan - Alamjan Nematilaev, walks around the dusty roads under the Russian sun, oblivious of his swollen abdomen. Unaware of his condition, his mother lets him play around with the other children. She had noticed the abnormal bulge on his belly, but ignores it, thinking he has rickets and that it will go away. Two weeks later, Alamjan complains of severe stomach pains and his parents rush him to the hospital. The horror on his parents' face is indiscribable when they learn that their child has been carrying another child inside him. Nothing can prepare them for this.

This is the base story of the Discovery Channel rerun I watched, of a feature aired February 2004 titled "Vanishing Twins." The show made me uneasy, but it intrigued me at the same time. And it got me interested because I had always felt as though I had a twin. As I watched one of the doctors pull out (reacd: deliver) the cause of Alamjan's discomfort, I asked myself, "What is that thing?"

It had an almost human shape, having a distinguishable head with growing lush dark hair, a body, limbs, and even fingers. Because it was discovered encased in a thick leathery membrane and it had what was similar to an umbilical cord connecting it to Alamjan's body, my inclination was to conclude that it was another human being, living inside the boy's body. However, I also knew it was physically impossible for a man to carry another human being inside him (as in the case of a pregnant woman), so what much more could a little boy? I felt like watching the stuff of nightmares.

Teratoma

Teratoma or teratoblastoma, also called teratoid tumor - this was the first explanation suggested in the show for the boy's condition. I grew up in a family with half a dozen doctors throwing medical terms at each other every family reunion and I had heard of the word teratoma before. Teratoma is caused by the development of independent germ cells which can manifest as lumps of flesh accompanied by the presence of hair and sometimes teeth. Teratomas can be malignant and therefore, cancerous. If the growth inside Alamjan were actually teratoid tumor, he must undergo treatment.

"Teratoma is caused by the development of independent germ cells which can manifest as lumps of flesh accompanied by the presence of hair and sometimes teeth."

But there are other explanations. As the show continues, the teratoma is set aside while the narrator states the possibility of a multiple birth disorder. The thought of it sends me chills me to this very moment.

Fetus in fetu

The fetus in fetu is a condition so rarely documented that it has become almost a medical anomaly. In 200 years of modern medicine, it has been recorded only 87 times. Just as its name suggests, a fetus in fetu is--be ready for this--a fetus inside another fetus. It begins in the first stages of embryonic development. When a a fertilized egg cell, or zygote, splits into two, under normal circumstances it forms healthy identical twins. In the fetus in fetu, one of the daughter cells malfunctions. This may be chromesomal or hormonal but for now there is no way of preventing it. As the normal cell develops, it becomes a disc, afterwhich it forms a cylinder, before wrapping around the abnormal cell. This condition is carried on throughout the embryonic development.

The normal embryo continues its development into another human being. Meanwhile the unhealthy embryo creates a comfortable environment within its twin, forming a placental analogue very similar to the amnion that protects fetal birds and reptiles and attaching a fleshy cord to its twin through which it draws sustenance. While the healthy embryo develops a heart, the fetus in fetu does not. To survive, it takes oxygen and nutrients from its host. Inevitably, the fetus in fetu becomes a parasite, literally sucking the life off its unfortunate victim.

I imagine the struggle of a normal embryo against the fetus in fetu similar to a star revolving around a black hole. The star emmits heat and light, which the black hole perpetually drains. The process goes on until the star exhausts its fuel and fades into the darkness of empty space.

"While the healthy embryo develops a heart, the fetus in fetu does not. To survive, it takes oxygen and nutrients from its host..."

Left undiagnosed, the healthy fetus can die of cardiac failure as its tiny heart pumps blood for two individuals. This was probably the fate of many "binary fetal systems" before the medical use of ultrasonic scanning. "Oh my baby died, it must be the curse of the witch doctor or the work of evil spirits!" But thanks to the power of modern technology we don't have to hear anything like that anymore. Nowadays many women go to hospitals, clinics or health centers for a medical check-up as soon as they realize they are pregnant. In the rare case of a fetus in fetu a pregnant woman expects twins, only to wonder later why she has a singleton instead.

The Vanishing Twin

When a doctor flies to Kazakhstan from Canada to examine the growth taken out of Alamjan she excludes teratoma. She performs an autopsy on the piece of human-shaped flesh and is amazed at the tissue formation having the qualities of a fetus. When local surgeons ask whether it is human, she assures them it is not. She then cuts the flesh in half she shows them that it lacks a heart and a brain and that its internal organs are absent--outside Alamjan's body, it didn't have the chance of surviving. Taking it out was the same as extracting a ruptured apendix or amputating a gangrenous limb. She confirms that for now, the boy is free of cancer. The growth is a fetus in fetu and neither the boy's mother nor the his father should be blamed for what happened. It was all circumstantial.

As the show ended I could see the sun set in the background while Alamjan plays with the other children, oblivious of what happened to him, another day awaits him. Before Vanishing Twins concluded I heard the narrator mention how 1 out of 8 pregnancies are twins, most of them just stops developing and are absorbed back to the body. That night I asked myself: "What happened to my twin?"

I will never know the answer.

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