Monochorionic twin pregnancies.

The monochorionic placenta should be considered a developmental malformation and, as such, represents one of the most common birth defects. Great strides are being made to unravel the progression of nature's successful attempt at human cloning through fission. Critical to any strategy to reduce the perinatal morbidity and mortality associated with monochorionic placentas is early detection. Intense surveillance in at risk pregnancies will provide a better understanding of their natural progression, improve the prognosis with early intervention, and ultimately provide the key to prevent many of the complications unique to the monochorionic placenta.