Month: March 2009
Twins.
Twins are two offspring resulting from the same pregnancy, usually born in close succession. They can be the same or different sex. Twins can either be monozygotic (MZ, colloquially “identical”) or dizygotic (DZ, colloquially “fraternal” or “non-identical”).
The general term for more than one offspring in the same pregnancy (multiple birth) is multiples; a fetus which develops alone in the womb is called a singleton. There are estimated to be approximately 125 million human twins and triplets in the world (roughly 1.9% of the world population), and just 10 million monozygotic twins (roughly 0.2% of the world population and 8% of all twins). The current rate in the United States is 31 twin births per 1,000 women.
















