It is indeed a double blessing for a parent who has twins, but it is also double the trouble. Raising twins can seem tough at times, but there are also some amazing things about having twins. Fraternal twins are the most common type of twins, and they do not share the same genes. Here, you can find out more about the different kinds of twins, how they are interesting and some surprising fraternal twin facts.
Fraternal twins or non-identical twins are either of a pair of twins who, as a result of developing from separate fertilized ova, are genetically distinct and not necessarily of the same sex or more similar in appearance than other siblings.
Fraternal twins in the womb, therefore develop after some special adaptations during foetal development.
You may be wondering now how they are different from identical twins? To start with identical twins are born due to fertilization of one singular egg with a sperm, whereas fraternal twins are born due to the fertilization of two sets of eggs.
Monozygotic twins (also known as identical twins) share 100% of the same gene whereas dizygotic twins (non-identical twins) share only 50% . This is similar to the genetic familiarity found between siblings born at different times.
It is common to have a fraternal twin set with one of each gender as opposed to the same gender. For example, in 100 births there will be at least 2 fraternal twins making them more common than identical twins.
Dizygotic twins are the scientific name given to fraternal twins. ‘Di’ means two and ‘zygotes’ means fertilized eggs.
The fraternal twins have two different amniotic sack in the womb. They also have a separate placenta. This is medically called as being dichorionic-diamniotic (Di means two). The two different sacks ensure equal chances of survival for the twins.
In a fraternal twin pregnancy, the first step that occurs is two eggs or ova are fertilised by the same sperm and produce two genetically different foetuses. They share only 50% of the DNA making them siblings who could have also been born years apart.
Researchers have shown that having twins depends largely on the mother’s genetic side and if they include fraternal twins, then the chance of having them are higher.
Apart from this many other factors help increase the chances of fraternal twins. Some of them are:-
Do fraternal twins look alike? Yes and no. Because they share 50% DNA, they look similar just like any other brother or sister. How we look is completely controlled by chromosomes from how tall we are, to the colour of our eyes, hair and so on thereby making them look as close to alike as possible. Your twins are also born at the same time, same age and at the same rate so its normal for them to grow up together and look similar.
A fraternal twin pregnancy can be something that you know because of intuition. Some women may even have dreams that they are pregnant with non-identical twins. You may even feel more nauseous than other pregnancies in the first trimester itself. High levels of intolerance for certain foods, smells, textures like meat, seafood, coffee can also be a sign. The most obvious one will be you will look ‘large for dates’ that is from early on itself which is a clear indicator of a twin pregnancy. Frequent urination is more magnified when you are having twins. Higher levels of hCG more, than a single pregnancy is also another factor.
A fraternal twin pregnancy week by week can be broadly divided into early and later development.
In the first 8 weeks of fraternal twin pregnancy each fertilized egg has started developing into hundreds of cells having layers, attached to different sides of the womb. They have their own amniotic sac and start developing body parts and organs. By 8 weeks they have arms and legs that bend, their hearts are beating, and they start developing the nervous system
By 12 weeks they start kicking and stretching, their fingernails start growing and also eyelids over their eyes. By 16 weeks they have unique fingerprints. They also start peeing out the amniotic fluid that they start have swallowed. By 20 weeks they start getting hair.
By 24 weeks eyebrows start growing. The twins also have a full set of tooth buds for the teeth to come in after birth. By 28 weeks the twins can open eyelids, layers of fat are building under their skin and smoothing out. They can suck on their fingers. By 32 weeks the twins are fully formed with arms, legs, torso and have a full head of hair by now. They are ready to be born in a couple of weeks
One must be cognizant of the many risks involved in a twin pregnancy. Some of them are
Some unique facts about fraternal twins you may not be aware of:
Twins are rare, and every parent should count themselves lucky if they have them. Enjoy the journey of parenthood and focus on keeping your infants healthy and happy.