When it comes to twins, there are two main types that people often refer to: fraternal twins and paternal twins. These two types of twins have distinct differences in terms of how they are conceived and develop.
Conception Process
Fraternal twins, also known as dizygotic twins, occur when two separate sperm cells fertilize two different eggs. This results in two unique embryos developing simultaneously in the womb. On the other hand, paternal twins, also known as monozygotic twins, begin with the fertilization of one egg by one sperm. After conception, the zygote splits into two separate embryos, leading to the development of paternal twins.
Genetic Relationship
Due to the separate fertilization of two eggs, fraternal twins share about 50% of their genetic material, much like any siblings born at different times. In contrast, paternal twins, arising from a single egg, share nearly identical genetic makeup, making them more genetically similar than fraternal twins.
Physical Resemblance
Fraternal twins may or may not look alike, similar to any siblings who share half of their genes. In the case of paternal twins, the genetic similarities often lead to striking physical resemblance, causing them to look almost identical to each other.
Growth and Development
During pregnancy, fraternal twins gestate in separate amniotic sacs and have their own placentas. This individual environment can result in different growth rates and sizes between the two siblings. Conversely, paternal twins typically share the same amniotic sac and placenta, leading to more similar growth patterns and sizes.
Health Risks
While both types of twins are generally considered healthy, they may face certain risks during gestation. Fraternal twins have similar health risks as regular siblings, such as prematurity or low birth weight. In contrast, paternal twins have a slightly higher risk of complications like twin-to-twin transfusion syndrome due to sharing the same placenta.
Twinning Rate
It is essential to note that fraternal twins are more common than paternal twins. The chance of having fraternal twins varies among populations and can be influenced by factors such as maternal age and family history. Paternal twins, though less common, occur spontaneously with a consistent rate across populations.