[abousoun]

Originally Posted by mr_j

there is a perfectly good reason why this does not occur, whatever it is so what happened in this case doc?

This is what I found in Wikipedia :

Superfetation is the formation of a fetus while another fetus is already present in the uterus.

It can occur only where there are two uteri, or where the menstrual cycle continues through pregnancy.

Reports of superfetation occurring long after the first impregnation have often been treated with suspicion and some have been clearly discredited. Other explanations have been given (and demonstrated) for different levels of development between twins.
Artificially induced superfetation has, however, been demonstrated although only up to a short period after insemination.

Religion: Superfetation is cited in the Talmud in the tractate Niddah, saying that a woman may use contraception during pregnancy to avoid the compression and destruction of her fetus by a possible second one.

Thank You ...