Twins: myth or fact?

There are many myths about twins. Here, we help you separate fact from fiction.

Myth: Twins run in families

Fact: There is no evidence that identical twins run in families. However, it is possible that a family could have a genetic predisposition to non-identical twins. For more information, see "Twins skip a generation" below. Other factors that make non-identical twins more likely are not genetic and include:

• Ethnicity. Twins are more common in black populations. Some studies have also reported that rates are lower in Korean, Thai, Vietnamese and Japanese people. Rates for white populations and Asian-Indians are somewhere in the middle.
• Maternal age. The older the mother, the higher the chance of twins.
• The higher the number of children you already have, the more likely you are to have twins.
• Infertility treatment. All treatments that stimulate the ovaries or involve multiple embryo transfer increase the risk of multiple births.

Myth: Twins skip a generation

Fact: It is a common misconception that twins skip a generation in families. You may have heard, for example, that if your father is a twin but you're not, you're more likely to have twins yourself. There's no evidence to support this.

However, some women may have a genetic predisposition to hyperovulation, where they produce more than one egg during a menstrual cycle. This makes it more likely that they will have twins. If this is the case, twins are just as likely to be born to each generation as they are to skip one.

Myth: Having lots of morning sickness means you’re pregnant with twins

Fact: Not necessarily. Although some mothers expecting multiple births report lots of morning sickness, other mothers who are pregnant with twins or more don’t experience any morning sickness.

Myth: Twins speak their own secret language

Fact: Twins have an innate understanding of each other and, as a result, may speak in their own code. Also, because they spend so much time together, one may pick up words said wrongly by the other twin that they both understand, which can be perceived as a twin language by other people. 

Myth: All pregnancies start out as twin pregnancies

Fact: It isn’t true that all pregnancies start out as twin pregnancies. However, thanks to early pregnancy scans, it has been discovered that more pregnancies than we thought do start out with two fertilised eggs.

It's possible that if you're scanned before 12 weeks, you'll see two foetal heartbeats and two foetal sacs, but one will have disappeared by the 12-week scan. This is because one of the embryos failed to thrive and it has been reabsorbed into the womb. This is referred to as vanishing twin syndrome and has no physical effect on the surviving baby.