Twins or twins? Learn their differences
When a family receives the news of a multiple pregnancy, one of the first doubts that arise is: are they twins or twins? Although in everyday language they are often used synonymously, the truth is that there are important biological differences between the two terms. Understanding them is not only interesting, but also helpful in better understanding the development of pregnancy and the potential medical implications.
What are twins?
Identical twins (also calledmonozygotic) come from a single egg fertilized by a single sperm. This zygote splits into two genetically identical embryos. That's why they share 100% of their DNA and are always of the same sex.
Embryo division can occur at different times, which determines whether or not they will share the same placenta or amniotic sac. This classification is very relevant from a medical point of view, since some cases have a higher obstetric risk, such as monoamniotic monochorionic twins, who share everything.
"Most monozygotic twin pregnancies share the same placenta, which requires special vigilance by the medical team."
And the twins?
Twins (also called dizygotic) are formed when two different eggs are fertilized by two different sperm. They are, therefore, siblings who develop in the womb at the same time, but share only 50% of the genetic material, like any sibling born at different times.
They can be the same sex or different sexes, and each has its own placenta and amniotic sac, which usually means a pregnancy with fewer shared risks than twins.
Twins share the same genetic origin, while twins come from different eggs.
How do you know if they are twins?
During pregnancy, an early ultrasound can help determine whether it is a monozygotic or dizygotic pregnancy by looking at the number of placentas and amniotic sacs. However, it is not always easy to distinguish them, especially if the ultrasound is done late.
If in doubt, genetic testing can be performed after birth to confirm whether babies share 100% of DNA (twins) or only 50% (twins).
What factors increase the likelihood of having twins?
Multiple pregnancies can occur naturally or through fertility treatments. Odds vary:
- Identical twins do not depend on hereditary or external factors. They occur randomly, in about 3 out of every 1,000 births worldwide.
- Twins, on the other hand, are more likely if: there is a family history of twins on the mother's side, the mother is over 35 years old or assisted reproductive techniques, such as IVF, are used.
According to the U.S. National Institute of Child Health and Human Development (NICHD), the use of fertility treatments has markedly increased the incidence of multiple pregnancies in recent decades.
Emotional and practical implications
Having twins can generate intense emotions: surprise, joy, anxiety... And also practical challenges. Simultaneously raising two babies requires support, organization, and a lot of patience. Although there are medical differences between twins and twins, on a day-to-day basis what counts most is the love and care they receive.
"It doesn't matter if they are twins or twins: each baby is unique and needs to be looked at as such."
Guidance information