In Vitro Maturation (IVM): Retrieving Immature Eggs and What It Means for Your Cycle

How IVM differs from conventional IVF

In conventional IVF, the patient takes daily gonadotropin injections for 8 to 14 days to grow multiple follicles to maturity inside the ovaries. Eggs are retrieved when they are already mature (metaphase II) and ready for fertilization. The stimulation phase is the most medication-intensive, expensive, and side-effect-heavy part of the IVF process.

In IVM, the patient undergoes minimal or no stimulation. Eggs are retrieved at an immature stage, typically germinal vesicle (GV) or metaphase I (MI), and are then matured in the lab using specialized culture media that contain hormones and growth factors designed to replicate the maturation process. Once the eggs reach metaphase II in the lab, they are fertilized by conventional IVF or ICSI.

The potential advantage is obvious: dramatically less medication, fewer injections, lower cost, and near-zero risk of OHSS. The challenge is that in vitro maturation is less efficient than in vivo maturation. Not all immature eggs successfully mature in the lab, and those that do may have slightly lower developmental competence than eggs matured inside the body.

Who IVM is designed for

PCOS patients with high follicle counts. Patients with polycystic ovary syndrome often have 30 or more antral follicles, placing them at very high risk of OHSS with standard stimulation. IVM eliminates this risk almost entirely because the ovaries are not stimulated to produce high estrogen levels.

Urgent fertility preservation. Cancer patients who need to start chemotherapy within days rather than the two to three weeks required for a full stimulation cycle may benefit from IVM. The retrieval can be done with little or no lead time, preserving eggs that can be matured and frozen for future use.

Patients who have experienced severe OHSS previously. For patients hospitalized for OHSS in a prior IVF cycle, IVM offers a way to retrieve eggs without repeating the risk.

IVM is generally not recommended as a first-line approach for patients with normal ovarian reserve who tolerate stimulation well. The lower per-cycle efficiency compared to standard IVF means more cycles may be needed to achieve the same cumulative result.

The maturation process in the lab

After retrieval, immature eggs are placed in IVM culture medium containing FSH, LH or HCG, and other factors that promote maturation. The eggs are incubated for 24 to 48 hours. During this time, the embryologist checks for extrusion of the first polar body, which indicates that the egg has reached metaphase II and is ready for fertilization.

Maturation rates in experienced IVM programs are typically 50 to 80 percent, meaning that roughly half to three-quarters of retrieved immature eggs successfully reach maturity. Of those that mature, fertilization and embryo development rates are comparable to standard IVF in some studies, though slightly lower in others.

Newer biphasic IVM protocols, which use two sequential culture media with different hormone compositions, have improved maturation rates in some centers. This is an active area of research, and protocols continue to evolve.

Success rates and what the data shows

IVM pregnancy rates have historically been lower than conventional IVF, with clinical pregnancy rates in the range of 30 to 40 percent per transfer in experienced centers compared to 50 to 60 percent or higher for standard IVF in comparable patient populations. However, these comparisons are complicated by patient selection: IVM patients are often higher-risk or different populations than standard IVF patients.

Live birth rates from IVM have improved over the past decade as culture systems and protocols have been refined. Some experienced centers report outcomes approaching those of conventional IVF for selected patient groups, particularly young PCOS patients with abundant follicles.

The small number of centers offering IVM worldwide means that the technique's potential may not yet be fully realized. Outcomes are highly dependent on lab experience, and a center doing five IVM cycles per year will likely have different results than one doing fifty.

Limitations and open questions

IVM remains a niche technique for several reasons. The lower efficiency per cycle means patients may need more cycles, which can offset the cost savings from reduced medication. The technique requires specialized lab skills and culture systems that not all clinics possess. And the long-term health data on children born from IVM, while reassuring so far, is less extensive than for standard IVF.

An open question is whether eggs matured in vitro are epigenetically equivalent to eggs matured in vivo. Some research has suggested differences in gene expression patterns, though no clinical consequences have been identified. This is an area of ongoing investigation.

For patients considering IVM, the most important factor is the experience of the center. A clinic that has performed hundreds or thousands of IVM cycles with documented outcomes is a very different proposition from one offering it as a new service with limited experience.

Evidence changes. Ask your clinician what has changed since you last reviewed your plan.

Related: From Fertilization to Blastocyst: Day-by-Day Development