There are two types of twins – identical or monozygotic (one egg), and non-identical or dizygotic (two eggs) twins. ​Identical twins form when one egg has been fertilised by one sperm and the zygote splits into two. What increases the chance of twinsFamily historyA woman has a slightly higher chance of having twins if she has a family history of twins. A family history of twins on the mother's side increases this likelihood more than a family history on the father's side. Racial backgroundIn the U.S., Hispanic women are less likely to have twins than non-Hispanic white women or black women, according to the ASRM.

Source: Standard Digital April 18, 2019 11:48 UTC