After retrieval, the first number patients often hear is how many eggs were collected. However, that number is only the starting point. The real goal is to retrieve as many mature eggs as possible.
Not every retrieved egg is mature
During retrieval, multiple eggs may be collected from the ovaries, but not all of them are ready to be frozen. Maturity means the egg has reached the right developmental stage.
Every egg retrieved does not reach maturity because the follicles do not all grow at the exact same rate. There may be variations in sizes, but most will be in the correct range to be mature at the time egg retrieval. The clinician will trigger at the best time based on follicular development to obtain the most mature eggs from the patient's growing follicles. This is why patients are carefully monitored the days leading up to egg collection.
A mature egg has reached the proper developmental stage and is biologically ready to potentially be fertilized one day.
Assessing egg maturity
Embryologists determine an egg’s maturity by identifying whether an egg has an extruded polar body. This indicates that the egg is at the metaphase II (MII) stage, where these eggs are considered mature.
Eggs that remain in earlier developmental stages are considered immature, including metaphase I (Mi) and germinal vesicle (GV) eggs.
Only mature eggs are usually frozen. Once mature eggs are identified, clinics typically freeze only those mature eggs because those can potentially be used later for family building.
Jullin Fjeldstad, VP of Clinical Embryology & Scientific Operations at Future Fertility, holds a BSc in Biology from the University of Victoria and an MSc in Clinical Embryology from the University of Leeds, UK. With over a decade of experience in the lab, she began her career in 2007 at the Victoria Fertility Centre, quickly progressing to senior embryologist and laboratory director. She now focuses on the clinical implementation of Future Fertility's innovative AI-based tools, scientific collaborations, and sharing research at international fertility conferences.
