Polyzygotic

Polyzygotic is an adjective used in biology and medicine to describe processes or conditions that involve multiple zygotes. In human reproduction, polyzygotic twinning refers to the development of two or more genetically distinct embryos from separate fertilized ova. The more common term for this phenomenon is dizygotic or fraternal twinning when two zygotes form; triplets or higher-order multiples result from three or more zygotes.

Polyzygotic twinning occurs when more than one ovum is released and fertilized during a single cycle. This can happen naturally or as a result of fertility treatments that increase ovulation or fertilization rates. Each zygote typically implants separately and, in many cases, each embryo has its own placenta and amniotic sac. However, placental arrangements can vary, especially in higher-order pregnancies, where two or more zygotes may share placental tissue or membranes.

Prevalence of polyzygotic twinning varies by population and maternal factors. Dizygotic twinning is more common among certain ethnic groups and ages; advanced maternal age and family history can increase risk. Fertility therapies that induce ovulation or enable implantation of multiple embryos substantially raise the likelihood of polyzygotic pregnancies.

Clinical considerations for polyzygotic pregnancies include a higher risk of obstetric complications such as preterm birth and low birth weight, and the management often requires specialized prenatal care. The term “polyzygotic” is less common in everyday clinical usage; it is typically discussed in reference to polyzygotic twinning or multizygotic conceptions, in contrast with monozygotic (identical) twinning.