There are two types of twins – identical (monozygotic) and fraternal (dizygotic). To form identical twins, one fertilised egg (ovum) splits and develops two babies with exactly the same genetic information.
Sometimes a woman's ovaries release 2 eggs, and a separate sperm fertilises each egg. This forms twins. These twins are called fraternal twins, dizygotic twins (meaning two zygotes) or non-identical twins.
It is estimated that 1 in 250 natural pregnancies will naturally result in twins. While twin pregnancies can happen by chance, there are some factors that may increase your odds of having two babies at the same time.
Fraternal twins are also called dizygotic twins.
Di-di twins
Both identical and fraternal twins can be di-di, or dichorionic-diamniotic, though all fraternal pairs are of this type. Di-di twins each have their own placentas and amniotic sacs, sharing only the womb to develop.
Such twins, known scientifically as 'MoMo', an abbreviation for monoamniotic-monochorionic, are some of the rarest types of twins, making up less than one percent of all births in the United States, noted the statement. It also stressed that such MoMo twin pregnancies have a high risk of fetal complications.
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.
Monochorionic Monoamniotic Twins
These types of twins share the same chorion, placenta and amnion. This is the rarest type of twin pregnancy – only affecting 1 in every 100 sets of identical twins – and it comes with a higher risk of complications because the foetuses can get tangled in their umbilical cords.
The quick answer to this question is that, in a twin pregnancy, it is the mother's genes that determine twins. First up, giving birth to identical twins is not genetic, but conceiving fraternal twins is. The mother may have the genetic trait of releasing two eggs in one menstrual cycle.
And because the death rate in the womb is higher for twins than for singleton births, female twins are more common than male twins.
They come from the same fertilized egg and share the same genetic blueprint. To a standard DNA test, they are indistinguishable. But any forensics expert will tell you that there is at least one surefire way to tell them apart: identical twins do not have matching fingerprints.
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.
You're more likely to have a vaginal birth if the first twin is in a head-down position. But there may be medical reasons why a vaginal birth is not recommended. If you have had a caesarean section before, for example, it's not usually recommended that you have a vaginal birth with twins.
A Colombian woman has given birth to a baby whose abdomen contained the tiny, half-formed — but still growing — body of her own twin sister. This type of birth, an example of “fetus-in-fetu,” is very rare but not unprecedented.
In humans, twins can result either from the ovulation and fertilization of two oocytes with the outcome of dizygotic twins (DZT) or from the splitting of a single embryo at some stage of its early development, resulting in monozygotic twins (MZT).
#1 Fraternal twins can be conceived as much as 24 days apart
For this reason, fraternal twins can be conceived a few weeks apart, though they generally will be born at the same time.
There is one particular power though which twins possess, longevity. Fraternal twins live longer than singletons and identical twins longer still. Male identical twins on average, saw the most benefit.
On September 1, sisters Umeno Sumiyama and Koume Kodama turned 107 years and 300 days old, officially breaking the record for the world's oldest living identical twins. The Japanese siblings are also the oldest identical twins to have ever lived.
Valentina Vassilyeva and her husband Feodor Vassilyev are alleged to hold the record for the most children a couple has produced. She gave birth to a total of 69 children – sixteen pairs of twins, seven sets of triplets and four sets of quadruplets – between 1725 and 1765, a total of 27 births.
Homopaternal superfecundation is fertilization of two separate ova from the same father, leading to fraternal twins, while heteropaternal superfecundation is a form of atypical twinning where, genetically, the twins are half siblings – sharing the same mother, but with different fathers.
The word for twins in Italian is gemelli (masculine, singular: gemello; feminine, singular: gemella).