Q89: Other congenital malformations, not elsewhere classified

Q89.4: Conjoined twins

A pregnancy with twins can occur if, for example, a fertilized egg cell divides into 2 embryos. The egg cell usually splits into 2 quite separate embryos. If the embryos do not completely separate in the womb, they stay connected to one another at certain parts of their bodies. For example, the twins can be fused at the head, the chest or the behind. The twins may also share organs or body parts.