Nearly five decades ago I was born 16 weeks prematurely which fostered an interest in medical mysteries. Over the years I've learned of a few pregnancy related anomalies that could of happened to anyone.
The first condition is Human Chimerism also known as Vanished Twin Syndrome. This unusual occurrence is the result of a twin pregnancy where one fetus absorbs the other very early in a pregnancy. Yes, one twin gets absorbed by the other resulting in one baby that effectively becomes a blend of itself and its sibling (2 different DNA's). The DNA cells that are acquired can live in any part of the healthy fetus.
The merger can result in many different manifestations to include mix matched reproductive organs or two different skin, eye and hair colors. This unfortunate pairing even occurs with opposite genders. Most human chimeras never know they are two-in-one. The discoveries are typically made when an unsuspecting chimera fails to match relative donors for medical procedures, paternal DNA discrepancies, or developmental abnormalities. I once read that an adult female chimera reported feeling her vanished sister's emotions.
Another rare phenomenon is called mosiacism, a condition where genetic errors occur during early cell division in a pregnancy resulting in 2 different cells from one fertilized egg. A person with this condition will have cells that contain different genetic makeup affecting the skin, blood cells and even reproductive cells. Researchers currently believe this condition is not solely spontaneous they feel this trait may also be passed down from a parent. Mosiacism is often referred to as a type of chimerism.
If you found the first two conditions peculiar you may find Microchimerism even more interesting. It is a fact that pregnant women circulate more than nutrients, they actually traffic fetal cells. This can include the circulation of cells from previous pregnancies if applicable. Healthy fetal cells have been found in the organs including the hearts and brains of their mother's. Our children literally stay in our hearts and on our minds. Science has discovered that mothers have transferred healthy fetal cells to others siblings.
The cells transfer and even grow without being rejected and can remain for decades or longer. A 94 year old woman was found to have her son's DNA which she carried for over half a century. Considering this phenomenon it appears many women could be considered microchimeras since they carry their own cells, their mothers and children's. One last note on microchimerism, it has also been discovered in organ transplant recipients after organ transplant surgery.
There is another unique condition known as superfetation this is when a woman conceives a second baby while already pregnant. The embryos are typically conceived weeks apart, will have different due dates and can even have different fathers.
The last unusual occurrence is an Hydatidiform mole or molar pregnancy a pregnancy that results from a genetic error which causes the rapid growth of tissue and cells and not a fetus.
Sometimes genetic anomalies occur that are obvious and other times they are concealed. One factor is constant in pregnancy and that is women are truly complex beings.
RESOURCES:
Embryogenesis of chimeras, twins and anterior midline asymmetries, Charles E. Boklage
Human Reproduction, Volume 21, Issue 3, 1 March 2006, Pages 579–591
Sons DNA Shows Up in Moms Brain, Live Science
Are Mothers Unconsciously Influenced by Foetal DNA That Lingers for Years After Pregnancy?
Mosiac Mutations May Not Be Rare
https://www.the-scientist.com/?articles.view/articleNo/43177/title/Mosaic-Mutations-May-Not-Be-Rare/
From Many One
We Are Multitudes
Medical Definition of Superfestation