My younger sister was born with 1 “and a half” kidneys, 2 bladders, 2 colons, extra teeth (she lost her front teeth twice in grade 1 in order to get her “adult” teeth), and was missing 2 half pieces of vertebrae. Any suggestions on what couldv’e happened to cause this?
IANA doctor, but my understanding is that a lot of this kind of thing can happen randomly. Just as fully viable identical twins can form early on by extra cell division of a single blastomere (see Stage 2 here), individual organs can have the same thing happen at (not much) later stages of pre-natal development.
Mutations in the womb are very common. I had eight wisdom teeth. A friend of mine was tested to donate a kidney to her sister. She passed every test but one–she only had one kidney.
Now that’s just bad luck! One sister with kidney failure, and her best chance for a match only has one… damn!
Spontaneous mutations during cell division (and there’s a lot of that going on when making a baby!) are incredibly common. Sometimes the cell’s corrective mechanisms can catch the mistakes and correct them, but not always. Also, if both parents carry certain genes, if luck should have it that they both appear in the child at once, certain birth defects or abnormalities can occur; I had a brother die at 2 days old due to a genetic defect that led to him not having a diaphragm, and therefore having underdeveloped lungs and heart.
There are also environmental things that can get in the way; certain medications or other chemicals that the mother may have been exposed to during her pregnancy may have been teratogenic. If your mom worked with chemicals, ideally she would have been reassigned to tasks that have little to no contact with them, but I’ve heard of places even today that don’t have reassignment plans for pregnant women.