Natural Cycle IVF: Its History at USC Fertility
USC Fertility is pleased to announce that is has launched a new study examining natural cycle IVF (in vitro fertilization). In Part One of a three-part blog about this exciting new project, we present a brief history of the treatment.
Natural cycle IVF is very similar to standard in vitro fertilization, but just without the use of medications to stimulate the ovary to make multiples eggs. Patients are monitored in a natural cycle with ultrasounds and blood work to track the growth of the dominant follicle. An egg retrieval is then performed when the dominant follicle is determined to be an appropriate size. The egg that is retrieved is then fertilized in the laboratory in the same way as traditional IVF. If an embryo is produced and continues to develop, it is transferred back to the uterus, again in the same manner as conventional IVF.
Natural cycle IVF has recently made a resurgence, gaining worldwide attention as an alternative to conventional IVF for both normal and poor responders. Natural cycle IVF has several advantages over standard IVF, including no risk of ovarian hyperstimulation syndrome (OHSS), very low or no costly and cumbersome gonadotropin injections, lack of production of excess embryos, and the elimination of multiple pregnancies. In the late 1980s—a decade after IVF was first introduced with gonadotropin stimulation—natural cycle IVF became a popular option for patients, though little was published in the literature to support its use.
USC Fertility was one of the first programs to publish its experience with different aspects of natural cycle IVF, and we released our success rates in 1989, 1990, 1992, and 1998. In the 1992, study we found that although the pregnancy rate was one half of that in stimulated cycles, the per embryo implantation rate was higher in natural cycle than in stimulated cycles.
In that same series, the average egg total aspirated per cycle was 1.6 as some secondary eggs were collected at the time of the aspiration in addition to the dominant egg. Of all the eggs that were collected, 72% of the dominant eggs were fertilized normally and 41% of the secondary eggs were fertilized normally with regular insemination. Fertilization of the secondary eggs was surprising, as many of these follicles were less than 10 mm. All of the pregnancies reported from that series were singleton pregnancies, though in 25% of the cases more than one embryo was available for transfer. The implantation rate per embryo was the same in both single embryo transfers and multiple embryo transfers, suggesting that the embryos from the secondary follicles had the same chance of implanting as those from dominant follicles.
In our experience published in 1992, a GNRH antagonist was used in the late follicular phase to block pituitary gonadotropin secretion—thus preventing the LH surge and early ovulation prior to retrieval. Because the GNRH antagonist blocks all pituitary secretion, a small amount of exogenous gonadotropin was administered in order to continue follicular development. Some researchers have therefore coined the term “minimal stimulation IVF.”
Based on our experience in 1992, we concluded that natural cycle IVF could be considered as a viable option for patients. Given the absence of the cumbersome and costly injection medications, minimal ultrasound monitoring, and absence of ovarian hyperstimulation syndrome (OHSS), patient acceptance of the natural cycle IVF treatment is high.
In 1998, we published the results of a study that followed women undergoing natural cycle IVF in order to examine further the contribution of immature oocytes. In this series, 101 immature oocytes were obtained during 59 follicle aspirations. Two pregnancies resulted from the transfer of embryos derived from immature oocytes when no other embryos were transferred. Therefore, we were able to show that immature oocytes may be retrieved successfully during the mid-cycle aspiration of the dominant follicle in unstimulated IVF cycles and that these immature oocytes can contribute to the overall pregnancy success of unstimulated IVF cycles.
That was the beginning…. Stay tuned to hear more about what we have learned since 1998.