The probability in my family of having twins is VERY high. Statistically I could be next in line. Statistically…
Both my grandmothers are from a set of twins, and we have 6 set of twins between cousins and their kids. (combining both families)
A twin is one of two offspring produced in the same pregnancy. Twins can either be monozygotic (“identical”), meaning that they develop from one zygote that splits and forms two embryos, or dizygotic (“fraternal”) because they develop from two separate eggs that are fertilized by two separate sperm. In contrast, a fetus which develops alone in the womb is called a singleton, and the general term for one offspring of a multiple birth is multiple. The twin birth rate in the United States rose 76 percent from 1980 through 2009, from 18.9 to 33.3 per 1,000 births.
The Yoruba have the highest rate of twinning in the world, at 45-50 twin sets (or 90-100 twins) per 1,000 live births, possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may stimulate the ovaries to release an egg from each side. The world’s highest rates of twinning are found across Central Africa, where there are 18-30 twin sets (or 37-62 twins) per 1,000 live births. In Latin-America and South Asia and South-East Asia the lowest rates are found; only 6-9 twin sets per 1,000 live births. North America and Europe have intermediate rates of 9–16 twin sets per 1,000 live births.
Due to the limited size of the mother’s womb, multiple pregnancies are much less likely to carry to full term than single births, with twin pregnancies lasting only 37 weeks (3 weeks less than full term) on average. Women who have a family history of fraternal twins have a higher chance of producing fraternal twins themselves, as there is a genetically linked tendency to hyper-ovulate. There is no known genetic link for identical twinning. Other factors that increase the odds of having fraternal twins include maternal age, fertility drugs and other fertility treatments, nutrition, and prior births.
(thanks to Mamafratelli for keeping having twins real…)