Two types of twins and complications of being pregnant with twins

The two main types of twins are identical (monozygotic) twins and fraternal (dizygotic) twins. Know more about it here.

Twins are a fascinating aspect of human biology and have captivated people’s imaginations for centuries. Know more about the types of twins and the complications you might experience if you’ll get pregnant with twins. 

Types of twins

There are two main types of twins: identical (monozygotic) twins and fraternal (dizygotic) twins. Identical twins result from a single fertilized egg splitting into two embryos. While fraternal twins result from two separate eggs being fertilized by two different sperm.

These two types of twins differ in terms of their genetic makeup, physical characteristics, and other traits. While there are some other rare types of twinning, they are much less common than identical and fraternal twins.

There are two main types of twins: identical (monozygotic) and fraternal (dizygotic).

types of twins - twin babies

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What are Identical (monozygotic) twins? 

Identical twins, also known as monozygotic twins, are twins who develop from a single fertilized egg that splits into two embryos during the early stages of pregnancy. As a result, identical twins share the same genetic material and are of the same sex.

Identical twins are the result of a random natural occurrence and are not influenced by any external factors. They occur in about 3-4 per 1000 live births and are more common in certain populations, such as African Americans and older mothers.

While identical twins share the same genetic material, they are not always physically identical. They may have differences in weight, height, hair color, eye color, and other physical characteristics. In some cases, identical twins may also have different personalities and temperaments.

Identical twins are typically formed when a single fertilized egg splits into two embryos within the first 14 days after conception. The embryos then develop separately, each with its own amniotic sac and placenta. In rare cases, the split may occur later, resulting in conjoined twins.

Because identical twins share the same genetic material, they are more likely to have the same blood type, tissue type, and other genetic traits. This can make them valuable subjects for scientific research on genetics and human development.

types of twins - twin babies

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What are Fraternal (dizygotic) twins?

Fraternal twins, also known as dizygotic twins, are twins who develop from two separate fertilized eggs that implant in the uterus at the same time. These are the most common type of twins, accounting for about two-thirds of all twin births.

Fraternal twins can be of the same or different sexes and share approximately 50% of their genetic material, just like siblings born at different times. They can have different physical characteristics, including different eye colors, hair colors, and facial features.

Fraternal twins result from the release and fertilization of two separate eggs during a single ovulation cycle. This can happen naturally in women who ovulate more than one egg at a time. This is more likely to occur in women who are older, have a family history of fraternal twins, or have used fertility treatments.

Fraternal twins develop in separate amniotic sacs and can have separate placentas or share a single placenta, depending on how the fertilized eggs implant in the uterus. Because they develop from two separate eggs, fraternal twins can have different genetic traits, including different blood types and different inherited conditions.

While fraternal twins are not identical, they may share a special bond due to their close relationship and shared experiences in the womb. Fraternal twins are also valuable for scientific research on genetics and human development. As they provide a natural control group for studies comparing identical and fraternal twins.

Complications of being pregnant with twins

types of twins - a pregnant woman

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Being pregnant with twins is considered a high-risk pregnancy, and there are several complications that can arise. Here are some of the potential complications of twin pregnancy:

  • Preterm labor and delivery

Women carrying twins are at higher risk of delivering early, which can increase the risk of complications for the babies.

This is a potentially life-threatening condition characterized by high blood pressure and damage to organs such as the liver and kidneys. Women carrying twins have a higher risk of developing preeclampsia.

  • Gestational diabetes

Women carrying twins have a higher risk of developing gestational diabetes, which can lead to high birth weights and delivery complications.

  • Twin-to-twin transfusion syndrome

This occurs in identical twins who share a placenta and blood vessels. One twin receives more blood flow than the other. Which can lead to complications such as heart failure or brain damage.

  • Intrauterine growth restriction

This occurs when one or both twins are not growing at the expected rate. This can lead to complications during delivery or after birth.

Women carrying twins are more likely to require a c-section delivery. Which can have its own set of risks and complications.

  • Postpartum hemorrhage

Women carrying twins are at higher risk of postpartum hemorrhage due to the larger placenta and increased blood loss during delivery.

  • NICU stay

Twins are more likely to require a stay in the neonatal intensive care unit (NICU) due to their increased risk of complications.  

It’s important for women carrying twins to receive early and regular prenatal care and to discuss any concerns or potential complications with their healthcare provider.

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