quadruplet

Quadruplets are a type of multiple birth, meaning more than one offspring are delivered in a single birth event. This is generally considered unusual and abnormal for humans, though it occurs with decreasing frequency from twins on up. Quadruplets can arise from a single fertilized egg (monozygotic) or multiple fertilized eggs (dizygotic). The specific mechanisms for monozygotic quadruplets can involve the separation of embryonic cells at various stages of development, sometimes leading to a single zygote dividing multiple times. While rare, multiple births like quadruplets carry increased risks for premature birth and subsequent health problems for the infants.12