When you announced your pregnancy, perhaps someone made a joke about twins running in the family. Or maybe you’ve always wanted twins and are trying to figure out the likelihood of it happening. Alternatively, perhaps you’re getting older and hoping to make your dreams of a big family come true by having multiples!
Whatever the reason, you’re in the right place, as we have the information to answer all your questions, including the one that brought you here — do twins skip a generation?
You may have heard that twins run in families, but is this true? Are you really more likely to have twins if other members of your family have had them?
Well, your chances of twins depend on many factors, including the type of twins that have appeared in your family and whether you’re the person contributing the sperm or the eggs.
Non-identical, fraternal (dizygotic) twins are more likely to run in families. This may be due to genes that can cause those with eggs and a uterus to release more than one egg during ovulation, also known as hyperovulation.
Hyperovulation can occasionally occur among those who don’t regularly release multiple eggs or have a history of twins in the family. Researchers haven’t yet been able to isolate the gene or genes responsible for this.
Even though researchers haven’t pinpointed the cause, some people are at an increased likelihood of having twins. According to The American Society for Reproductive Medicine, women who are fraternal twins have a 1 in 60 chance of having twins, and men who are fraternal twins have a 1 in 125 chance of fathering twins.
It was previously believed that identical (monozygotic) twins were random — not genetic. However, some scientists now believe that
So, your family history may increase your chances of having identical twins, too. However, the chance of having identical twins run in your family is rare. Only around 3 or 4 in every 1,000 births are identical twins.
There’s no skipping when it comes to inherited traits, they just might not always be evident.
If you notice that your family (or someone else’s family) has a history of twins but seems to have skipped a generation, the likely cause is that the person who could have carried the so-called twin genes that generation was male.
Since the birth of fraternal twins involves the person with eggs contributing extra eggs during ovulation, male family members wouldn’t necessarily have an increased chance of having twins, as they’re responsible for the sperm in the equation — not the eggs.
However, any female children of twins could inherit a combination of genes that makes them more likely to release multiple eggs during ovulation (thanks to the DNA passed from their dad). This would make them more likely to have twins and give the appearance of the twins skipping a generation.
While they won’t guarantee a twin pregnancy, a variety of factors can increase the likelihood of finding yourself pregnant with multiples, including:
- Age. Women over age 30, especially those in their late 30s, have an increased chance of twin pregnancies, as their bodies are more likely to release multiple eggs. Women age 35 to 40 who have already given birth have an even higher chance of conceiving multiples.
- Race. Certain races have historically produced more twins than others. For example, Black and non-Hispanic white women statistically have more twins than Hispanic women. Meanwhile, women of Japanese ancestry have the lowest prevalence of twins.
- Weight and height. Larger women (this can mean women who are taller, have more weight, or both) are more likely to have a non-identical twin pregnancy. While more research is needed, one theory is that larger individuals intake a greater amount of nutrients.
- Folic acid supplements. Some research indicates that supplementing with folic acid while trying to conceive may increase your chances of getting pregnant with multiples. Yet, this theory comes from small studies and hasn’t yet been confirmed in a larger study. Regardless, taking folic acid when trying to get pregnant can help protect your baby’s brain development, so it’s worth taking.
- Prior twin pregnancies. If you’ve conceived fraternal twins naturally before, you’ve proven that your body can release multiple eggs close enough together to conceive twins. This puts you at a higher-than-average chance of it happening again.
- Fertility treatments. According to the American Society for Reproductive Medicine, twins will occur in about 1 out of every 250 pregnancies naturally. The rate of having twins is much higher in women who get fertility treatments. The same organization estimates that about 1 out of every 3 pregnancies with fertility treatments will be multiples.
Why are the chances of twins so much higher with fertility treatments? Many fertility drugs work by increasing the number of eggs the ovaries produce, thus increasing the chance of multiple eggs being released and fertilized to produce fraternal twins.
Additionally, as part of in vitro fertilization (IVF), a woman may be implanted with multiple embryos to increase the likelihood of one implanting. While this raises the likelihood of becoming pregnant, it also increases the chances of having twins.
Having twins may seem about as likely as winning the lottery. After all, only an estimated 3 percent of pregnancies per year in the United States are multiples.
If you’re hoping to expand your family by two, you may have found yourself looking back over family trees to see whether there are any signs of twins in your genetic pool. While there’s no way to guarantee yourself a pair of twins, having a history of twins certainly won’t hurt your chances.
Don’t have twins in your family tree? Depending on your age, genetics, and even the fertility treatments you may be trying, your chance of having twins might just be higher than the average. So, if you have your heart set on two little bundles of joy, you may be pleased to learn that other factors are leaning your direction.
Keep in mind that pregnancies involving multiples are higher risk and can come with more complications. If you find out you’re pregnant with multiples, you’ll want to discuss this with your OB-GYN so they can provide additional monitoring and support throughout your pregnancy and delivery.