You just have your ultrasound, and the Doctor say it’s a twin baby. How does a multiple pregnancy happen? Multiple pregnancies come from a single cell. But how this single cell develops into two babies? Twin pregnancy comes chance, but hereditary factor place a very important role in having a twin or multiple pregnancy. Fertility pills may also have an effect of having a twin babies.

There are only two kinds of pregnancy, the identical and the fraternal or what we call non identical babies. Multiple pregnancies may carry two or more fetus in the uterus. Identical twins happen when the two cells split during the time of zygote or during cell division. The identical twins have the same genotype or phenotypes, meaning they only have the same genetic factor. Their face is similar and basically they also have same sex.

Fraternal twins happen when a woman release two eggs and when these eggs are being fertilized by two sperm cells. Fraternal twins stays in a separate amniotic sac and have separate placenta while the identical twins share in one amniotic sac but separate placenta. They do not look a like. Their genotype and phenotype are different. Fraternal may have or may not have the same gender.

Siamese or conjoined twins are other variation of an identical twin. This happen when there is an incomplete splitting of the fertilized egg. Just like identical twins, Siamese also has same genotype and phenotype and both have the same gender.

Mirror twins. Is also one variation of identical twins? Mirror twins are vary rare and often times cannot survive long after birth. They are called mirror because they share organs of the opposite side, meaning if they are a baby boy, one baby will carry the one scrotum and the other bay will carry the half scrotum. One baby will have the left heart and the other baby will have the right heart. One baby will have the left arm and another baby will have the right hand.

During prenatal check up, pregnancy can be detected if it is twin or not. By the use of an stethoscope you can hear two fetal heart beat. Ultrasound and 3D will also show two fetus in the uterus.