Frequently Asked Questions about Twins

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In the answers to the questions below, the following words are synonyms and may be used interchangeably:
Identical twin = monozygotic = MZ
Fraternal twin = dizygotic = DZ
For more information about these terms, see the Zygosity section.

Occurrence of Twins

How often do twin births occur?

Why is the number of twins increasing?

Are there more male twins or female twins?

I am a twin. Do I have an increased chance of having twins?

Twins run in my family. Do I have an increased chance of having twins?

What factors are related to fraternal (DZ) twinning?

Does identical (MZ) twinning run in families?


Appearance of Twins

Can identical twins look different?

Do female identical twins appear more different than male identical twins?

Can fraternal twins look so similar that they are mistaken for identical?

Can a male/female twin pair be identical twins?

Can twins be of different races?


Types of twins

What are mirror image twins?

What is a “hidden twin”?

What are half-identical twins?


Medical Questions for Twins

What is twin-to-twin transfusion syndrome?

If my twin gets a disease, will I also get it?

What causes some twin pairs to be born with very different birth weights?


Fun Facts about Twins

Do identical twins have identical fingerprints?

Do identical twins always have the same hand preference?

Can twins have different birthdays?

Can twins read each other’s minds?

Can twins have different fathers?