The presence of a sponsoring embryo in a batch of poor quality thawed embryos significantly increases pregnancy and implantation rate.

Objective: To evaluate quantitatively the effect of one good-quality (sponsoring) embryo in a batch of low-quality thawed embryos on the implantation and pregnancy rates (PR).

Design: Retrospective analysis of data.

Setting: Tertiary care center IVF clinic affiliated with a university medical school.