Fraternal twins (also called dizygotic twins) result from the fertilization of two separate eggs with two different sperm during the same pregnancy. Fraternal twins may not have the same sex or appearance.
Fraternal twins can be the same or opposite sex and their genes are as different as any other brother and sister. Often, same-sex fraternal twins look different. For example, they might have different hair or eye colour. Occasionally they look quite similar.
Non-identical twins
Non-identical (dizygotic) twins happen when 2 separate eggs are fertilised and then implant into the womb (uterus). These non-identical twins are no more alike than any other 2 siblings. Non-identical twins are more common. The babies may be of the same sex or different sexes.
Like any siblings, fraternal twins are the products of two separately fertilized eggs from the same mother and father. They are genetically as similar as other non-twin siblings. By chance, they could look very similar, or very different, just as non-twin siblings can look very similar or very different.
These twins are no more genetically similar than siblings born years apart. The rates of non-identical twins differ between groups: it's about eight in 1,000 in caucasian populations, 16 in 1,000 in African populations, and four in 1,000 in people of Asian decent.
As per the university, MoMo twins are some of the rarest types of twins, making up less than one per cent of all births in the United States. According to Dr Gupta, MoMo twins account for “fewer than 0.1 per cent of all pregnancies and one per cent of identical twins”.
Monochorionic-monoamniotic twins are identical twins that share both a placenta and an amniotic sac. This is the rarest and highest risk form of twin pregnancies.
Understanding Monoaminotic 'Momo' Twins
Monochorionic twins are identical twins who share a single placenta. They represent around 70% of identical twin pregnancies. Monochorionic-diamniotic twins are identical twins who share a placenta, but each has their own amniotic sac.
Not only are Koen and Teun twins, they are the world's most least alike twins.
While there are risks associated with all twin pregnancies, dizygotic (fraternal) twin pregnancies usually bring about the least amount of complications, carrying the lowest risk of all types of twins. Worse complications are possible with monozygotic (identical) twins because the embryo is dividing.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.
Vanishing twin syndrome was first recognized in 1945. This occurs when a twin or multiple disappears in the uterus during pregnancy as a result of a miscarriage of one twin or multiple. The fetal tissue is absorbed by the other twin, multiple, placenta or the mother. This gives the appearance of a “vanishing twin.”
Fraternal twins live longer than singletons and identical twins longer still. Male identical twins on average, saw the most benefit. The rarity of twins has inspired many myths about them.
Most sets of Twins
1707–c. 1782), a peasant from Shuya, Russia, gave birth to 16 sets of twins.
Can twins have different fathers? In rare cases, fraternal twins can be born from two different fathers in a phenomenon called heteropaternal superfecundation. Although uncommon, rare cases have been documented where a woman is pregnant by two different men at the same time.
About 1 in 3 of all sets of twin births are vaginal births. You may choose to have an elective caesarean, or your doctor may recommend a caesarean section because of potential complications. Even if you plan a vaginal birth, you may end up having an emergency caesarean section due to complications during labour.
Are twins hereditary? Yes, some types of twins are hereditary, meaning that twins run in families. Heredity on the mother's side ups a couple's odds of conceiving fraternal twins. Fraternal twins are two babies from two different eggs that were released from the ovaries simultaneously.
1. While many people can't tell them apart, Mary-Kate and Ashley are not identical, but rather fraternal: Mary-Kate is one inch taller than her sister and is left-handed, while Ashley is right-handed.