Placental anomalies in a viable cloned calf.

Placental anomalies are associated with a high mortality rate in mammalian cloning programs. In this report, we detail the very unusual occurrence of a grossly abnormal placenta that supported a viable cloned calf to term. The placenta was recovered intact 3 h following birth, and its weight was within normal limits (4.3 kg). The chorioallantois of the cloned transgenic female Holstein calf contained only 26 cotyledons. Twelve of these were enlarged and functional. Six were poorly developed, and eight were degenerating. The 12 functional cotyledons ranged in diameter from 8 to 20 cm. The nongravid horn had six rudimentary (<5 cm in diameter) cotyledons and eight cotyledons that remained as oval, mineralized plaques. Despite the reduction in number of placentomes, there was no adventitial placentation. Although this report documents observations from a single case, it does show that a morphologically deficient placenta was able to support development to term and resulted in a viable calf.