Q: My husband and I are both twins. I am an identical twin, and he is a fraternal twin. What are our chances of having twins of our own?
A: Your chance of having twins is less than you might think. There are two different kinds of twins:
- Dizygotic or fraternal twins (2 separate eggs and sperm)
- Monozygotic twins (1 egg and sperm which split after fertilization)
The incidence of monozygotic twins is the same all over the world, it's 1 in 250 pregnancies. And no matter if you were a monozygotic twin or not, the incidence is still the same.
The incidence of dizygotic twins in general is 1 in 85 pregnancies, but it also depends on your ethnic background. People from Africa have a higher incidence and Asians have a somewhat lower incidence.
If you were a dizygotic twin then your chance of having another set of dizygotic twins depends mainly on your ethnicity and then it's likely a little higher. For the average person, it would increase probably from 1 in 85 to 1 in 50 pregnancies.
If you were identical twins or you previously had identical twins then the risk is still the same, it's 1 in 250. Your chance of having twins is not increased because you are an identical twin.
Here are the odds of having twins:
- 1 in 85 in general
- 1 in 250 has identical twins
- 1 in 17 if the mother is a fraternal twin
- 1 in 85 if the mother is an identical twin
- 1 in 10 when you take Clomid
- 1 in 2-3 if you have IVF
- 1 in 90 if you are Caucasian
- 1 in 60 if you are of African descent
- 1 in 150 if you are of Japanese descent
- 1 in 300 if you are of Chinese descent
- 1 in 8,100 to have spontaneous triplets
- 1 in 729,000 to have spontaneous quadruplets
- 3 in 4 to deliver triplets prematurely
- 1 in 2 to deliver twins prematurely
- Under 1 in 50,000 to have conjoined (Siamese) twins
- 1 in 2-3 to have both twins with head down (vertex) at birth