Is IVM Right for You?

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I see lots of articles about IVF, but I don’t see much out there about IVM (in vitro maturation). I haven’t been able to tolerate the IVF hormones, so I’m trying to go down a no/low hormone route for retrieving eggs, and I’d love to know what the success rates are with the existing IVM technology that’s out there.

—Anonymous

When we do IVF, we are hoping to retrieve mature eggs, meaning those that are capable of being fertilized. An egg becomes mature after being exposed to the hormones given throughout the IVF process. These hormones are meant to mirror the hormones our brains normally produce during our menstrual cycle to get a follicle, which contains the egg, to grow and eventually ovulate. With IVF, the levels of the hormones are higher than what our brain would normally produce, in hopes of getting multiple follicles to grow. These signals also serve to prompt the egg within that follicle to begin the processes that will eventually allow it to be fertilized with sperm. More specifically, the egg we hope to get with IVF has completed meiosis I and has only one set of chromosomes, allowing it to combine with the sperm, which also has one set of chromosomes, to make an embryo that has two sets of chromosomes.

With in vitro maturation (IVM), little to no medication is used, so the follicles have not had sufficient exposure to the signals that allow the egg to complete meiosis I by the time of the egg retrieval. The hope is that the egg has had enough hormonal signals to allow the egg to mature outside the body in the embryology lab and then be fertilized. While this approach does sound appealing, as it involves fewer injections, less monitoring, reduced time, and a lower risk of ovarian hyperstimulation syndrome, studies have not shown this approach to be as effective as IVF in achieving pregnancy.

For example, a 2020 study out of Vietnam compared patients undergoing IVF versus IVM. They randomized women with high follicle counts (over 24 follicles per ovary) to undergo either an IVM cycle or a traditional IVF cycle. After the first cycle, 35.2% of the women were pregnant in the IVM group as compared to 43.2% of women in the IVF group. After 12 months, cumulative pregnancy rates were 44% in the IVM group versus 66.2% in the IVF group.

There are several reasons why the pregnancy rates are lower. First, maturity of the egg is mostly related to the completion of meiosis I, which can be visualized under the microscope by an embryologist. However, there are also processes that need to happen within the egg that we cannot assess visually and could mean that even if combined with sperm, the egg will not be able to make an embryo. Second, immature eggs are bound more tightly to the wall of the follicle, meaning that in an IVM cycle, there will be some eggs that we do not get at the egg retrieval, as the egg will not separate from the wall of the follicle. All of this leads to less embryos available for transfer and, in turn, lower chances of becoming pregnant.

Although IVM may not be ready for “prime time” yet, there are exciting developments on the horizon. Ongoing research is being performed to try to identify optimal low-dose medication protocols and changes in the laboratory and culture environment that may help improve IVM outcomes.