Ovarian Tissue Freezing and Transplantation
- Category: Fertility Preservation
With this technique there is no need for ovarian stimulation. Typically, one ovary is harvested by an outpatient laparoscopic procedure which takes less than an hour. Because it is not practical to freeze ovary as a whole, the outer shell of the ovary which contains all the immature eggs is cut into slivers and frozen in test tubes. The freezing is performed using a Slow Freezing protocol with the utility of a programmable freezer. While the surgery is brief, the process in the lab can take up to 6 hours and is a meticulous process. The ovarian freezing procedure can be done in children as it does not require sexual maturity. In adults, ovarian freezing is often times needed when there is insufficient time for performing ovarian stimulation to freeze eggs or embryos. Another advantage of this procedure is that it can restore hormonal functions after ovarian transplantation.
Ovarian Tissue Transplantation
When time has come to consider childbearing, ovarian tissue can be transplanted in two different ways, both developed by Dr. Kutluk Oktay. Dr. Oktay performed the world’s first pelvic ovarian transplantation procedure with previously cryopreserved tissue in 1999 which was reported in the prestigious New England Journal of Medicine in the year 2000. With that technique, ovarian slivers are thawed, and then they are reconstructed under a microscope, attached to a biodegradable scaffold and transplanted to pelvic side wall or the remaining ovary with a laparoscopic procedure. The transplant is similar to skin grafting, in that it reconnects to surrounding blood vessels on its own over the next 2-10 days. During that process more than 50% of eggs maybe lost and that is why transplanted ovary does not last as long as the natural ovary. Dr. Oktay has recently performed ovarian transplantation procedures with the aid of a Da Vinci robot which is expected to increase the precision of the surgical technique further and enhance graft survival. We are also working on some chemicals that can speed up new blood vessel formation. There have been around 20 livebirths reported from pelvic ovarian transplants but true success rates are unknown since the procedure is relatively new and number of unsuccessful procedures are not reported. For these reasons, ovarian freezing and transplantation are considered experimental. At our institution, they are performed under an Institutional Review Board (New York Medical College) approved research protocol.
Another technique developed by Dr. Oktay is transplantation under the skin (heterotopic transplantation), either in the forearm or abdomen area. This technique may be chosen when pelvis is not suitable because of prior pelvic radiation or scarring or when there is a need to closely monitor the graft (if there is any higher risk of ovarian cancer as in the case of BRCA-mutation carriers). The procedure is performed under local anesthesia and typically in the IVF laboratory. Hence it is much less invasive and lower cost than the abdominal transplantation. Disadvantages include the need for performing IVF since natural pregnancies cannot occur and lack of livebirths from the very few procedures performed thus far. Dr. Oktay and team reported embryo development using the eggs aspirated from ovary transplants under the skin which was reported in the leading medical journal of Lancet in 2004. In one case, transplantation of previously frozen ovarian tissue resulted in 4 consecutive pregnancies and 3 livebirths. The mechanism behind these spontaneous pregnancies remains a mystery. We speculated that the transplanted healthy ovary maybe pushing the remaining menopausal ovary into action but this remains to be proven. Under-the-skin transplantation is also experimental and done under a research protocol.
Preparation for Ovarian Transplant
Before we decide to transplant previously frozen ovarian tissue, we always thaw a test piece to assess the viability, egg density, and if there was a cancer diagnosis, to rule out any involvement of the tissue with cancer. This process may take several weeks. This is especially important if the tissue was frozen at an outside lab. We receive ovarian tissue from different states and countries. Arrangements can be made to transport previously frozen ovarian tissue from many other countries. We also prefer that you are on hormone replacement prior to transplant as this may improve the new blood formation in the grafts. Depending on the findings from egg density calculation and your age we may decide to transplant all pieces at once or may save some for later procedures.
What to Expect after Ovarian Transplant
Recovery is fast as this is an outpatient procedure. The grafts do not begin function for at least 8 weeks and sometimes it may take months before we can detect hormone production by blood tests, and egg development by ultrasound exams. We generally monitor you monthly by hormones test first, starting 8 weeks after the transplantation. Once hormone levels begin rising, we add ultrasounds to the monitoring.
Can I Conceive Naturally After Ovarian Transplants?
After pelvic transplants natural pregnancy is possible if your fallopian tubes are functional, not blocked or removed. However because transplanted ovaries may not last as long as the natural ovaries we are concerned that you may lose your egg reserve while trying naturally. That is why we generally recommend IVF to speed up the process.