Obstetrics

Multiple Pregnancy

Twin and triplet pregnancy is higher risk than singleton pregnancy; early determination of chorionicity and amnionicity drives surveillance, fetal-medicine referral, preterm-birth prevention and timing and mode of birth.

Definition

Multiple pregnancy is a pregnancy with more than one fetus. It is classified by chorionicity, the number of placentas, and amnionicity, the number of amniotic sacs; these determine fetal risks, surveillance, referral and timing and mode of birth.

First principles

Chorionicity and amnionicity drive care

The clinically important classification is the number of placentas and amniotic sacs, not simply whether twins are identical. Shared placental circulation and a shared amnion create additional fetal risks.

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