There has been good debate on what is the correct number of eggs to be retrieved and number of embryos to be transferred during an IVF cycle. The debate revolves around success rate and cost of the procedure and patient comfort and compliance. I will try to address the first of these two questions, i.e. whats is a good number of eggs to retrieve during an IVF cycle and how should one go about it.
Technically speaking, a single egg has the potential for fertilization and the first IVF baby was born from a natural cycle IVF. But, not every egg gets fertilized on being exposed to sperms and not all embryos have the potential to result in a pregnancy. This inherent failure of assurance of pregnancy resulting from the transfer of a single embryo (fertilized egg) after IVF has resulted in evolution of the practices of artificially inducing the ovaries to produce many eggs in a cycle and of transferring more than one embryo into the uterus. However, even these interventions do not guarantee success of the IVF cycle and the outcome of such IVF cycles can also be measured only in terms of probability.
What is the standard IVF practice?
The standard practice is to give daily hormonal injections to induce the growth of many eggs (targeted number of eggs varies from 5-6 to up to 10), which is coupled with strict monitoring using ultrasounds and blood tests. This process is often very stressful and unfriendly for the patient. This also entails a risk of some complications due to the stimulation which can be short term and may have some long term sequel as well.
What are the disadvantages of conventional stimulation protocols for IVF?
The conventional stimulation protocols have following disadvantages-
- Patient discomfort associated with daily injections
- Risk of complications like ovarian hyperstimulation, which occurs as a result of recruitment of excessive number of follicles.
- In patients with poor ovarian reserve, higher dosage of hormones may not yield more eggs because stimulation helps in recruitment of follicles already present in the ovaries.
- Quantity does not correlate with quality – Retrieval of a larger no of eggs may not necessarily mean better quality of eggs. In fact, many of these eggs may be of poor quality and some may even have aneuploidy.
- Excessive production of hormone Estradiol (produced by a larger no of growing follicles) has a negative impact on the endometrial receptivity, i.e. the ability of endometrium to allow implantation of the embryos. This may negatively affect the outcome of the cycle.
What is minimal/ mild stimulation IVF?
Minimal/ mild stimulation strategy aims to optimally stimulate the ovaries to produce a few (typically 2-7) follicles, rather than bombarding them with hormones in order to produce a larger numbers of follicles. This strategy yields a smaller no of follicles, but these follicles are optimally primed to grow and are likely to be healthier. These protocols use either only oral medications or a combination of oral medications and lower dose of hormones given for a shorter duration. Mild stimulation strategies are specially beneficial for IVF in women, who are at higher risk of hyper-stimulation or are known poor responders.
What are the advantages of minimal/ mild stimulation IVF?
Minimal/ mild stimulation IVF, sometimes also called as micro IVF or mini IVF offers several advantages to select group of patients. These include-
- The minimal/ mild stimulation protocols are more patient friendly as they require relatively lesser medical intervention.
- Minimal/ mild stimulation is more physiological and in sync with woman’s natural cycle.
- Growth of lesser number of follicles means a less steep rise in the levels of hormone Estradiol, as a result of which endometrium is likely to be more receptive, thus achieving good pregnancy rate despite of lesser number of eggs.
This is the time to reconsider ovarian stimulation strategies for IVF, so that a good pregnancy rate can be balanced with more physiological and patient friendly treatment.