What is Natural IVF?
Natural IVF refers to IVF which uses fewer drugs that traditional IVF, and works within a woman’s own natural cycle. Conventional, high stimulation IVF uses drugs to shut the menstrual cycle down (‘down-regulation’) before re-starting it again, and uses high doses of stimulating drugs to grow lots of follicles. Natural IVF however does not shut the cycle down but works within it, and the process is focused on collecting the one follicle naturally selected by the body. In Natural Cycle IVF, no stimulating drugs are used and in Modified Natural IVF, small amounts of drugs are used to support the growth of this single follicle.
The ‘Quality vs Quantity’ debate
Historically, the focus in IVF treatment has been to collect as many eggs as possible, in order to maximise success rates. However, Natural IVF moves away from this approach and instead focuses on the quality of eggs. This is because of the way a woman’s body works. In a normal cycle, the ovary produces several follicles that are capable of being released. At some point, one follicle becomes dominant and uses the body’s resources to grow and become the egg that is released, while the other follicles shrink back and ultimately die. Stimulating drugs will not create new follicles, but they might encourage existing follicles to grow larger rather than diminish in size and die; however these are not the ‘front runners’ that the body has selected. They therefore often have chromosomal abnormalities and are unable to fertilise or implant. This is the reason that often collecting a greater number of eggs is not always ultimately more successful, as the final number of eggs that are actually viable is the same. It is especially true that for patients who don’t typically respond to stimulating drugs, a higher dose will not help as extra follicles cannot be created from nowhere. For these patients it is more effective to focus on the follicle that has been selected by the body, and to collect this at the right time rather than use unnecessary drugs, which will affect the womb environment for implantation.
What makes Natural Cycle IVF different to conventional IVF?
|4-6 weeks duration||2 weeks duration|
|4-5 weeks of medication||No stimulating drugs|
|Recommended 3 month break between cycles||No break between cycles|
|Collects as many eggs as possible||Collects one or two eggs|
|Cycle is shut down and then re-started||Cycle is not interrupted|
|Focuses on quantity of eggs||Focuses on quality of eggs|
|Often not viable for those with low ovarian reserve||Allows those with low ovarian reserve to try with their own eggs|