Fetus in Situ medical condition not known

In the movie's beginning the two doctors are perplexed and astonished at what appears to be a developing fetus on the lower back of Karen's neck. Not believing what they see, both physicians keep their tentative diagnosis from Karen.

The doctors had no explanation or name for the phenomenon.

But today in 2016 they would have. It is called, "fetus in situ". Apparently there is historical medical evidence for this but it was very scant and for some reason kept much under wraps. But in the last ten years and thanks to the Internet, medical evidence of, "the cannibalized twin" has popped up everywhere. Google it and there's medical cases that date back just two or three years.

The 'fetus-in-situ' medical condition happens in the pregnant mother's womb when a developing early fetus completely overwhelms and ingests another fetus, which is either an identical or fraternal twin. The enveloped twin tries to survive, sometimes for a while as a parasite but it cannot last this way. Eventually it dies. Sometimes the body calcifies it in the mother's abdomen where it becomes known as a, 'stone baby'. At other times the cannibalized fetus can end up in other parts of the body, even the skull. This happened to a 26 year old graduate student from India who was in the U.S. Another cannibalized twin showed up near the belly button of a man in England. Another cannibalized fetus showed up in the lower abdomen of a British woman living in Cyprus, having the same black hair as the British woman. The scariest incident was that of man in India who in 2006 was found to have been carrying his growing twin inside him all his life, leading to the village kids teasing him about being pregnant. The kids never knew how close to the truth they were. The man's in-situ twin had survived by being a viable parasite. It grew to alarming proportions. When doctors opened the man's abdomen, the doctor was shocked to find a human hand with long finger nails emerging. It was something out of a horror movie. The victim recovered completely and returned to his home village, free of the tremendous pain and discomfort and being able to breathe normally again, as well as having lost the huge bulge in his belly. The village kids teased him about finally having given birth to the baby. Again those kids were closer to the truth than they knew.

Incidentally, in some of these cases, the persons felt some kind of sorrow for having lost an identical twin. In the others where the victim experienced excruciating pain, they were glad to get rid of it.