
Originally Posted by
Verst Eltone
unbelievable!!! is there any biological explaination why this happens

Source:
How Twins are Made - Twin Pregnancy - How You Get Pregnant With Twins
* Multiple eggs are released or there is more than one ovulation. Both (or more) eggs are fertilized and you have fraternal twins. This can happen with or without fertility drugs.
* One egg is release but splits in two. Identical twins are made. This can happen with or without fertility drugs.
* In cases of IVF, there are usually 3 or more fertilized eggs put back into the uterus. The rationale is that not all of these will implant, though sometimes they do.
Once conceived you have a lot of possibilities on placentas, implantation locations, number of amniotic sacs. For example, you can have two babies, two placentas, and two sacs. You can have two babies one placenta, two sacs. It will be important to know exactly what you are dealing with, particularly when it comes to amniotic sacs.