Frozen embryo transfer outcome according to reason for freezing the embryos

To determine if cryopreservation influences pregnancy outcome following transfer.

Retrospective cohort analyses of frozen embryo transfer (ET) cycles divided into five different categories according to reason for freezing.

Frozen embryos remaining as a result of failing to conceive with the previous fresh transfer or those remaining because of cancellation of fresh ET related to inadequate endometrial thickness, result in lower pregnancy rates (PRs).

The fact that embryos never deselected in a group whose fresh ET was canceled because of risk of ovarian hyperstimulation did not have the best results suggests that these oocytes may not be of equal quality to those attained with a more modest response.