Conjoined twins

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Definition Symptoms Causes

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Definition

Twins have long been a source of interest and fascination.

Fraternal (dizygotic) twins occur when two separate eggs are fertilized by two different sperm. Identical (monozygotic) twins occur when a single fertilized egg splits and develops into two fetuses. In a few cases, identical twins fail to completely separate into two individuals. These babies are known as conjoined twins.

Conjoined twins may develop in as many as one in 50,000 pregnancies, but conjoined twins account for only one in about 250,000 live births. Female conjoined twins outnumber male conjoined twins at a rate of three to one.

Conjoined twins are most often joined at the chest, head or pelvis. In some cases, conjoined twins share one or more internal organs. At times, conjoined twins can be surgically separated. The success of separation surgery depends in part on where the twins are joined and how many organs are shared.

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Symptoms