A more contemporary way to perform a cryo (frozen) embryo transfer is the modified natural embryo transfer protocol. The concept behind this is to simply perform a frozen embryo transfer at the proper time point during a natural ovulatory menstrual cycle to allow for embryo implantation and development. During such a treatment cycle, the patient’s natural follicle development is followed by ultrasound and blood work. At the time that it is expected that the woman would ovulate, a trigger shot of hCG is typically given to cause ovulation and promote good corpus luteal function, thereby maintaining proper progesterone levels. The day following the follicular trigger shot, a minimal form of Progesterone administration is typically begun. During the natural cycle no supplemental Estrogen is typically required. The advantage to such a cycle is that there is little need for hormonal support and implantation is ultimately allowed to occur in an environment very closely replicating a natural ovulation. Disadvantages to such a transfer cycle mainly focus on our inability to time the cycle to possibly desired calendar days for transfer, as we are simply following along the natural follicle development. Not all women will be candidates for a modified natural embryo transfer cycle. Those patients would include women with irregular menstrual cycles, history of recurrent pregnancy loss, gestational carrier cycles, and others. Better suited candidates are women who have had prior spontaneous successful pregnancies and now have infertility issues due to tubal factor or severe male factor. If such a frozen embryo transfer cycle interests you, please consider discussing this with your physician at the F.I.R.M.
By Michael L. Freeman, M.D.