What are the three types of twins
There used to be a time in the past when people understood nothing about the process of reproduction. A lot of myths and folklore surrounded it. The birth of multiple children simultaneously, twins, triplets, or more, was either considered a gift of god or a demonic presence.
Although we have come a long way from those superstitions, there are still numerous things we do not understand about the biology of twins. The birth of twins is increasing these days due to the advanced age at which mothers are conceiving. The increased use of assisted reproductive techniques also causes a woman to undergo multiple pregnancies.
Assisted reproductive techniques sometimes induce super-ovulation in a female ovary, causing it to release more than one egg in one cycle of menstruation. A misleading theory that is especially common about twins is that they are genetically similar, which isn’t always true.
There are different types of twins, and genetic identity differs accordingly. It is observed that heredity plays a significant role in this phenomenon; women who are twins often also give birth to twins. Moreover, there are still a lot of facts that have not been discovered or founded. Research has been going on in biology and genetics to know more about twins and pregnancy-related matters.
1. Fraternal twins
There are various types of twins, and one among them is a type called fraternal twins. Generally, people think that twins are always identical in nature, but it is not always true. Fraternal twins are also called as unidentical twins.
These twins do not just look different but are also different in their DNA. They are born from the same womb, but two different eggs from the mother are fertilized by two different sperm from the father. These children are no more similar than two siblings. You must remember that although they are called twins, yet they are not similar in nature.
The fetus of both twins is also separate within the uterus of the mother. They undergo independent individual placentation at different portions of the uterus. These twins are genetically unidentical. They are often also called dizygotic twins, as they are formed from two different zygotes. There is an equal probability of these twins being of the same gender as there is of their being of the opposite one.
So basically, there is no surety about the gender of the babies being the same or different. If both the non-identical twins are female, they are called sororal twins.
2. Maternal twins
Maternal twins are those that are identical in nature, both in look as well as genetically. This is the way laypeople understand the concept of twinning, only when the babies look alike.
These twins are formed from the same egg and the same zygote, which was split in two to form two individuals during the early days of formation. Thus they are also called monozygotic twins. These twins are necessary for the same gender, although their sexual identities may or may not differ.
So if one of the zygotes is transforming into a female, then the other one will also be a female. It is often noticed that identical twins are mirror images of each other, that is, the left half of one twin is identical to the right half of another and vice versa. Based on the growth stage at which the zygote split, these twins can have one placenta or two different ones in which they grow.
3. Half-identical twins
This is the third twin type, which explains why fraternal twins look alike sometimes. This theory, although it has no scientific evidence, is widely accepted. It is assumed that the egg in the mother’s uterus splits into two before fertilization.
Each egg gets fertilized by a different sperm of the father. Half of the genetic material is supposed to be the same in both the twins, thus leading to their almost identical looks. These twins are also referred to as sesquizygotic. The true biology behind why these fraternal twins look alike is yet to be discovered, but several presumptions surround it at the moment.
Although it is still a theory, it is very relevant in understanding the twins’ concept and their formation. Moreover, you never know when this theory will be scientifically proven and thus may be a fact afterward.
Twins do not always share the same placenta during the pregnancy. A twin pregnancy where two different placenta and amniotic sacs are present provide each growing fetus the necessary amount of nutrition required separately. There is a good chance that the no-sharing of nutrients will grow both of them healthy.
If there is only one placenta with two amniotic sacs, two identical twins are definitely growing in the womb. This pregnancy needs to be carefully monitored, as several medical issues might take place. Thus the mothers with this kind of pregnancy should be kept under observation so that there does not arise any complication.
The rarest type of twin-baby pregnancy is the one where both the babies are supported by a single placenta and a single amniotic sac, thus entirely dividing nutrition. There is a risk of several complications and especially that of the umbilical cords getting tangled up. Umbilical cords, if tangled, call cause harm to the baby and even may be dangerous. Thus, one needs to take full care in such a situation and recommend the doctor if necessary.
Often mothers carry certain misconceptions about twin pregnancy. Of course, the uterus will stretch larger, and the baby bump will be larger than most single-baby pregnancies, but this isn’t a clear indicator. The ultrasound is the only procedure that can properly show twin babies’ visuals, and every doctor will mention two heartbeats in the womb.
Mothers also do not require to consume twice the amount of food they would consume in normal pregnancy with a single baby. This misconception is there with a lot of women, and they try to consume more food, which ultimately affects their health.
Antara Chowdhury is a Content Marketer and Strategist with 6 years of experience. She is Master degree holder in Journalism and wants to explore everything she can write on.