health

Identical twins develop when a fertilized human egg splits into two separate
embryos during the first twelve days following conception. If the
split occurs after the twelfth day, the twins will not separate fully from
each other and will be conjoined at birth. The cause of most cases of
delayed splitting is not known; no genes have yet been identified that
lead to conjoined twins. There have been, however, about ten cases
reported in which conjoined twinning occurred after the mother had
been exposed to a drug given to stimulate ovulation or a drug used to
treat fungal infections.
The symptoms of conjoined twins depend on the location of the
fusion between the two twins and whether the twins are symmetrical
(equal) or not. In many cases the twins die shortly after birth from heart
failure, lung failure, or obstruction in the digestive tract.