Egg inside of the follicle is like a baby inside the womb
A microscopic egg is nurtured inside of the follicle, like a fetus inside the womb.
Term
A fetus has to be nurtured within the womb for 9 months “full term” to be delivered in optimal health. A baby delivered pre-term often has health issues. It was recently proposed that “term” also exists for an egg: it must be nurtured within the follicle for a certain number of days during the follicular phase (or ovarian stimulation) to attain the highest quality.
Term is important
Unlike for a pregnancy, the term for eggs cannot be defined by an exact number of days, because it varies from 9 to 18 days. But it is well known that as the follicular phase becomes shorter, fewer eggs will be of good quality. Even a four-day difference reduces egg quality by half!
Catch 22 of regular IVF
The success of modern conventional IVF is mainly due to fertility drugs that make a woman produce multiple eggs instead of one. But these drugs also accelerate follicles growth, making the follicular phase shorter.
More limitations of regular IVF
The egg itself is microscopic, but the egg-containing sac, follicle, can be easily observed on ultrasound. Therefore, in regular IVF, doctors use the size of the follicle and the level of hormone estradiol made by the follicle, to predict if the egg inside is ready for harvesting. However, the size of the follicle is an unreliable predictor of an egg’s quality, similar to how the size of a woman’s belly is unreliable in predicting her due date. Since estradiol is also produced by the follicle, it does not provide meaningful information about the egg.
Some patients are at particular disadvantage
This problem is particularly real for very young patients and patients with polycystic ovaries syndrome, because they tend to have a stronger response to fertility drugs. Patients over 37 have a shorter follicular phase, because their ovarian cortex has less collagen and follicles may begin to rupture spontaneously at a smaller size (vanishing follicles).
