We thank Dr. Horacio B. Croxatto from the Instituto Chileno de Medicina Reproductiva for his valuable comments in the preparation of this manuscript. This work received financial support from grants CONCYTEC 628 DE-89 and 2043 DE-91, and FONDECYT 1030315.

This investigation was supported by a grant from the Sciences and Technology National Council (CONCYTEC, project No. 2043), Lima-Peru.

Acknowledgments -This investigationw as supportedb y a grant from the Sciences and Technology National Council (CONCYTEC, Project No 2043) Lima-Peru.