If you or your partner comes from a family that's brimming with twins, you may be wondering whether that might influence your chance of having twins or multiples. The answer: It does — but only in certain cases.
Here's what you need to know about the science behind family heredity and twins.
Are twins hereditary?
Yes, some types of twins are hereditary, meaning that twins run in families.
Heredity on the mother's side ups a couple's odds of conceiving fraternal twins. Fraternal twins are two babies from two different eggs that were released from the ovaries simultaneously.
Some research has found that having fraternal twins in a mother's immediate family may double the chances of conceiving fraternal twins. One theory is that it's because a certain gene may predispose some women to "hyperovulation," or releasing more than one egg during each menstrual cycle. Women with this gene appear to have naturally higher levels of particular hormones, including those related to the regulation of releasing eggs.
However, few genes appear to be definitively linked to hyperovulation, so it could just be that genetics in general on the mother's side contribute to the probability of having fraternal twins.
Heredity on the father's side, on the other hand, does not increase a couple's odds of having twins. This is true even if his family is packed with multiples.
What about identical twins, or two babies who have an identical set of genes because they're from one fertilized embryo that splits in two? Most cases of identical twins don't appear to run in families and instead seem to be a spontaneous occurrence, say experts. But there are some families with a larger-than-usual number of identical twins, suggesting there may be a genetic link.
But such a link hasn't been proven definitively. In other words, there's no hard evidence that being from a family with identical twins has an impact on your probability of having identical twins yourself.
Read This Next
Do twins skip a generation?
If you've heard that twins skip a generation, the theory goes like this: If there is a hyperovulation gene and a man inherits it from his mother, he may pass this gene on to his daughter. His daughter, in turn, is then more likely to release more than one egg when she ovulates and therefore could conceive fraternal twins. So the twins could have, in essence, skipped a generation.
However, because there aren't any definitive links between genes and hyperovulation and because twins don't predictably always skip a generation, it's likely just a coincidence when it does occur. In reality, there is no solid evidence that twins skip a generation. So that notion is nothing more than a colorful myth.
How likely is it that you'll have twins?
About 3.2 percent of all live births in the U.S. in 2019 were to twins. So there's about a 3.2 percent chance that you'll conceive twins.
But a few factors — not just heredity — can up the chances of having twins, including the following characteristics in the mother:
- She is 35 or older
- She is overweight
- She's taking fertility treatments
- She's Black
- This is not her first pregnancy, especially if she's previously been pregnant with multiples
Yes 
No 
Trending On What to Expect
