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Fraternal Twins Facts

Fraternal Twins Facts
Fraternal twins, which are non-identical twins, are also referred to as dizygotic twins, biovular twins, dissimilar twins, and if both babies are female, they can be referred to as sororal twins. Fraternal twins develop when two different fertilized eggs implant in the uterus following conception. These eggs are fertilized by two different sperm cells, resulting in two babies from different eggs and different sperm cells. This is why they are not identical. Fraternal twins are essentially siblings that happen to grow in the womb at the same time and have the same birthday, sharing the same mother and father (usually) but not the same egg or sperm.
Interesting Fraternal Twins Facts:
Most fraternal twins also have separate placentas and amniotic sacs as well.
The most effective way to identify fraternal twins or identical twins at birth is to examine the babies' DNA.
If one baby is a boy and the other is a girl they are definitely fraternal twins because they do not have the same chromosomes. Boys have XY chromosomes and girls have XX chromosomes.
In order for fraternal twins to occur the mother must release two eggs. If this happens at the same time in one month this is called hyperovulation. When this occurs it is called superfecundation.
If the mother releases one egg and becomes pregnant and then releases another egg within 24 days she may become pregnant again with a second baby at the same time. Although the babies will be a different age they are usually born at the same time. This is referred to as superfetation. It is possible for the babies to have different fathers in this situation.
The highest rates of fraternal twins occur in Africa and the lowest occur in Asia. In Africa the rate is 14 or more fraternal twins per 1000 births and in Asia is approximately 6 fraternal twins per 1000 births.
Fraternal twins that are female have a 1 in 17 probability that they will also give birth to fraternal twins.
Women who release more than one egg a month may do so because of an inherited gene.
Some fraternal twins look very much alike while others are different in so any ways including hair color, eye color, personality, and even body shape and size.
Although fathers can carry the gene that cause hyperovulation, they do not have a higher chance of fathering fraternal twins because of it. They can pass the gene to their daughters, which can increase their chances of having fraternal twins.
Fraternal twins can also be the result of fertility treatments for couples that are having difficulty conceiving a child.
Other factors that can result in fraternal twins are the mother's age, diet, and the use of birth control pills. These factors can all result in hyperovulation and an increased chance of multiples.
The number of twins being born in the United States is rising and it believed to be because the increase in fertility treatments and possibly the growth hormones found in many foods today.


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