Many IVF programs routinely schedule frozen embryo transfers (FET) to occur on specific days by putting their patients on estrogen and progesterone to prepare the uterine lining for implantation. This allows for a flexible schedule for the clinic and the patient, i.e. it allows the clinics to group FETs together and avoid weekend transfer procedures. However, the patient must remain on both estrogen and progesterone to support the pregnancy for up to 12 weeks.

More and more, clinics are starting to schedule FETs in natural cycles, timed to natural ovulation with minimal medications. This does mean that a transfer can occur any day of the week. Due to tradition and convenience, some clinics remain hesitant to switch to natural cycle FETs. Part of the problem is that there have been very few studies showing what the success rates were in natural vs. programmed FET cycles. The few studies that have been published have reported on a fairly limited number of cycles.

Pacific Fertility Center has always been a proponent of natural cycle FETs. Because we do about 400 FETs each year, we have been able to gather a large number of cycles to evaluate. Most of our patients we evaluated for this study were in natural cycles but some patients had to do programmed cycles because they did not ovulate regularly or because they had to travel some distance to come to PFC for their FET and needed to have the more precise scheduling that a programmed cycle affords.

In our study, we looked at 1,378 frozen embryo transfers done between 2000-2005. Of these, 934 were done in patients using embryos from their own eggs and 444 were done in patients using embryos from donor eggs. The bottom line is that there were no differences in delivered pregnancy rates within both groups of patients (own eggs and donor eggs) between those patients having a transfer timed to natural ovulation or those patients with estrogen-progesterone uterine preparation.

Because we feel that a natural cycle is less costly, requires no blood tests and (usually) fewer ultrasounds and injections, patients find this a desirable alternative to the more common, programmed FET. In addition to these patient-friendly reasons for choosing natural cycle FETs, we now feel PFC has solid data to justify this approach.

Preliminary results of this study were presented at an oral presentation at the Pacific Coast Reproductive Society meeting in Palm Springs this past April (see sidebar).

This study has just been submitted to Fertility and Sterility, the major reproductive endocrinology journal of the American Society for Reproductive Medicine. We expect full publication after the peer review process is completed.

Carolyn Givens, MD

“Outcomes of Natural Cycles vs. Programmed Cycles for 1378 Frozen Embryo Transfers” Carolyn R. Givens, M.D.a, Leslie C. Markun,b Isabelle P. Ryan, M.D.,a Philip E. Chenette, M.D.,a Carl M. Herbert, M.D.,a and Eldon D. Schriock, M.D.a Submitted July 2007 to Fertility and Sterility.

Tags: Clinical Trials & Studies, Embryo Freezing, FET - Frozen Embryo Transfer, Success Rates, Treatment Options

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