In the United States, approximately one out of every 83 births results in twins. Among these twin births, about 72 percent are fraternal twins. Over the years, the number of fraternal twin births has significantly risen, from approximately 19 in every 1,000 births in 1980 to 33 in 2017. This increase can be attributed, in part, to the increasing success of in vitro fertilization, a method that is more likely to result in fraternal twins. However, while having twins brings double joy to parents, it also presents unique challenges throughout the entire journey of pregnancy, delivery, and childhood.
Fraternal Twins vs Identical Twins
When it comes to twins, there are two main types: fraternal twins and identical twins. While both types involve the birth of two babies at the same time, there are some key differences between them.
Identical twins are the result of a single fertilized egg splitting into two zygotes. This means that they share the same genes and are always of the same sex. Essentially, identical twins are genetic clones of each other. They have the same physical characteristics and often have similar personalities.
On the other hand, fraternal twins occur when two separate eggs are fertilized by two different sperm cells during the same pregnancy. This means that they are essentially siblings who happen to be born at the same time. Fraternal twins share about half of their genes, just like any other siblings. They can be of the same sex or different sexes.
It’s important to note that while identical twins are always the same sex, fraternal twins can be either the same sex or different sexes. This is because the fertilization of two separate eggs allows for a greater variation in the genetic makeup of the babies.
In summary, the main difference between fraternal twins and identical twins lies in their genetic makeup. Identical twins share the exact same genes and are always the same sex, while fraternal twins share about half of their genes, just like regular siblings, and can be the same sex or different sexes.
The Science Behind Fraternal Twin Pregnancy
Fraternal twins, unlike identical twins, are more commonly observed in the general population. This occurrence is believed to have a strong familial connection, indicating a genetic influence. The phenomenon of a fraternal twin pregnancy is thought to arise from a process called hyperovulation, where the ovaries release multiple eggs during a single menstrual cycle. In addition to genetics, certain factors such as advanced maternal age, ethnicity, and body composition may also contribute to the likelihood of conceiving fraternal twins.