When I learned that I am carrying twins, I was not that totally surprised. Almost everybody in the family in my husband’s side were actually expecting for twins. There are three sets of twins and one triplet in my mother-in-law’s side and two sets of twins in my father-in-law’s side. All of them are identical. And so, everybody thinks mine will be identical too.
I got a different kind of reaction from people who knew that I am carrying twins. They are extremely fascinated and expressed their excitement for the birth of my twins. I, on the other hand, got bombarded with the most commonly asked questions: Does twinning run in the families? Are they identical or fraternal twins?
Twinning can be influenced by a lot of factors:
1. Hyper ovulation: This is the only cause that can be identified as genetic, therefore a family history has a big role to play. This is the genetic tendency of the woman to release multiple eggs during ovulation, which become fertilized by two sperms at the same time, producing what we call as fraternal twins or dizygotic twins (two fertilized eggs called zygotes). Their genders can be a boy-girl, girl-girl, or boy-boy combination.
However, since only women ovulate, the hereditary issue is only valid on the maternal side. While men can carry the gene (they inherited from their mother who may have the genes) and pass it on to their daughters, a family history of twins doesn’t make them any more likely to have twins themselves, but their future daughters can. Such case makes it appear that twinning skips generations in families and this is purely circumstantial. If we look at the evidence of genetic hyper ovulation, it all depends whether their children are sons and daughters.
2. Splitting of the egg: This happens when a woman normally releases one egg during ovulation which is fertilized by a sperm, and the fertilized egg splits into two, resulting to identical twins or monozygotic twins. There is still no scientific explanation of the splitting. Hence, at this time identical twinning is considered a random event and do not run in families.
Identical twins have the same gender and blood type. The time of splitting of the fertilized egg determines if identical twins will share the same placenta, amnions, and chorions.
3. Use of fertility drugs: Multiple pregnancies (especially twinning) are on the rise in
recent years, and majority of the reason is the use of fertility drugs. Fertility
drugs induce the ovary to hyper ovulate, resulting to fraternal twinning.
4. In Vitro Fertilization (IVF): This is done by harvesting viable eggs from the mother and fertilizing it with sperm outside the uterus. The fertilized eggs (usually 3) are then put back into the uterus to allow it to grow until maturity. The rationale why several fertilized eggs are put back into the uterus instead of just one is to increase the chances of conceiving because not all will successfully implant. But if they do all implant, this will result to multiple pregnancies.
Frateral twins are more common than identical twins, accounting for about two-thirds of twins. The most common combination is the boy-girl combination, followed by the fraternal girls, then fraternal boys, then identical girls, and the least common- identical boys.
In my case, ultrasound revealed that they are both boys. For a couple of months, I rested my mind on the presumption that they are likely to be identical twins, until my grandmother revealed to me lately that her mother had a twin who died immediately after birth. That revelation would mean I have a genetic tendency to hyper ovulate, which can result to fraternal twins. Hence, the thrill is still high for everyone in the family as to what type of twins I am carrying. But, be it identical or fraternal twins, we will welcome them with so much joy in our hearts.