Do twins run in the family? Can twins come from the father’s side? These are interesting and common questions at there seems to be a lot of misunderstanding about. I will try to answer these questions as simply as possible.
Definition of Twins
Merriam-Webster’s definition of Twins is either of two offspring produced in the same pregnancy.
Identical Twins
Identical (monozygotic) twins do not run in the family. Identical twins are the result of ONE SPERM fertilizing ONE EGG that then splits into two (and sometimes very rarely, three)! This essentially means that the DNA of one embryo (one person) splits and creates two embryos (two people) with the same DNA. It’s fascinating! This is why identical twins look exactly alike!
Imagine when you were conceived…if your embryo split…there would be another person growing alongside you with your EXACT DNA makeup. Your IDENTICAL brother or sister.
Just because you have the same DNA though does not mean you will have the same personalities or interests as your identical twin. In fact, many identical twins have totally different personalities even though they look exactly the same!
Identical twins are always the same sex with a very, very rare exception of a condition called Turner’s Syndrome, which is a chromosomal condition affecting one of the X chromosomes in a female.
Identical twins happen spontaneously, regardless of whether “fraternal twins” happen to run in your family. I will get into fraternal twins in a moment.
According to multiple sources, the odds of having identical twins are about 1 in 250-300 but can vary slightly. It’s random and like winning the lottery. The likelihood of having fraternal twins is higher.
The odds of having identical twins when undergoing in vitro fertilization (IVF) are reported to be twice as frequent as with natural conception. For some reason, IVF embryos are more likely to split after implantation.
Fraternal Twins
Now let’s talk about fraternal twins (dizygotic twins) which are more common than identical twins due to a variety of scenarios that can increase the chances of having them.
The only way twins can “run in the family” is when a female in the family has a genetic disposition to hyper-ovulate due to a special gene she inherited. In other words, she is more likely to release more than one egg during ovulation. When this happens, each egg has the chance to be fertilized by a different sperm, resulting in two separate embryos being created at the same time. Essentially, two separate pregnancies develop at the same time within the same womb.
It is also possible for a woman to release more than one egg at a time without having the gene to hyper-ovulate. Women are more likely to do this as they get older, usually after 35, but it can happen at any age during the reproductive years.
Fraternal twins are as genetically alike as any two other siblings born years apart. They can be the same or different genders, have different hair and eye colors, different skin tones, noses and lip shapes, different body types, and different heights.
Do you have an older or younger sibling? Imagine you were both created at the same time and born together. That’s what fraternal twins are.
Many people believe that fraternal twins cannot run on the father’s side of the family. This is false and I can explain it easily. If a woman has a genetic disposition to hyper-ovulate, she can pass that gene directly to her son. She may have even inherited that gene from her father, who inherited the gene from his mother.
Make sense?
When that son grows up and has children of his own, he obviously cannot ovulate…however he CAN pass that gene along to his daughter, just like any other genes we receive from our parents, regardless of gender. If his daughter receives the gene, then she is likely to have the ability to hyper-ovulate and release more than one egg at a time, thus resulting in a twin pregnancy. This is how twins “run in the family”.
Another way to increase the chances of having fraternal twins is by using fertility treatments. Some medications will increase a woman’s chances of ovulating more than one egg. Medicine and hormones combined with other fertility treatments such as IVF (in vitro fertilization) and IUI (intrauterine insemination) significantly increase these chances.
Looking for more support with your twins? Twinsanity Life offers a range of support and advice to new twin parents. View my blog for more help!
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