Ovarian puncture, or also knows as the egg retrieval, is one of the key moments in an In Vitro Fertilization (IVF) treatment. It is the procedure through which developed eggs are extracted from the ovaries after hormonal stimulation. However, sometimes not all the eggs retrieved during the puncture are mature and capable of being fertilized in the lab. Why does this happen? Is it something to worry about? Can it be avoided?
What is an immature egg?
During the ovarian cycle, eggs mature inside the follicles. In order for an egg to be fertilized by a sperm cell, it must reach what is known as metaphase II (MII), which is what we refer to as a mature egg. When the egg is still in earlier stages, such as the germinal vesicle (GV) or metaphase I (MI), it is considered immature.
There are several factors that can influence whether or not the egg reaches this stage:
- Individual Ovarian Response
Each patient responds differently to the hormonal stimulation. Some may have a slower or uneven response, meaning not all follicles are at the same stage of maturity at the time of the egg retrieval.
- Egg quality
Age or ovarian reserve can affect the egg's ability to mature properly, even with optimal hormonal stimulation.
- Incorrect timing of stimulation or trigger shot
The timing of the ovulation trigger injection (hCG or LH analog) is crucial. That's why patients must follow medical instructions carefully—administering it too early or too late could prevent the eggs from fully maturing.
- Polycystic Ovary Syndrome (PCOS)
A woman with PCOS may have many follicles, but a higher proportion of immature eggs.
What can be done if there are immature eggs?
Each case must be addressed individually. Some of the strategies we use at IGIN include:
- Adjusting the hormonal protocol based on the individual response, with regular monitoring.
- Scheduling the egg retrieval at the exact right time, depending on follicle size and development.
- In vitro maturation (IVM): In some cases, immature eggs can complete their maturation in the lab.
It's important to note that obtaining immature eggs during an egg retrieval is not unusual. Typically, enough mature eggs are retrieved to proceed with the process confidently (usually around eight). Our goal is to maximize that proportion without compromising quality.