Multiple Births - Terminology

Terminology

• Monozygotic – multiple (typically two) fetuses produced by the splitting of a single zygote
• Dizygotic – multiple (typically two) fetuses produced by two zygotes
• Polyzygotic – multiple fetuses produced by two or more zygotes

Terms used for the order of multiple births in human beings are largely derived from the Latin names for numbers. Two offspring (twins) is the most common form, eight (octuplets) is the largest number ever successfully carried to full term with all children surviving.

• One offspring – singleton
• Two offspring – twins
• Three offspring – triplets
• Four offspring – quadruplets
• Five offspring – quintuplets
• Six offspring – sextuplets
• Seven offspring – septuplets
• Eight offspring – octuplets
• Nine offspring – nonuplets
• Ten offspring – decaplets
• Eleven offspring – undecaplets
• Twelve offspring – duodecaplets