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The Egg Retrieval: IVF Cycle Day “0”

Egg retrieval day is an exciting and anxious time. The success or failure of an IVF cycle depends on this moment. Embryologists know that everything the patient has gone through up to this day; from the first negative pregnancy tests to the infertility diagnoses, every shot, all the stimulation medications, all the financing, and trauma of infertility- all of it has been leading up to this day. The patient has been so INVOLVED up to this point, so seemingly “in control” (even if that is an illusion). But then you arrive at the clinic the morning of the retrieval, and it all out of your hands. It’s even out of your physician’s hands. Your eggs are about to pass through a tiny window, into the hands of scientists you have never met. The IVF lab is under strict lock and key. No one can enter that sterile environment without permission. Not even the physicians.


In pre-covid days, embryologists used to see patients briefly at the bedside pre-surgery, before they become groggy with anesthesia, to confirm your cycle plan with you. We discuss and confirm: How many eggs to be fertilized? How many to be frozen? We are doing PGT? How many embryos do you want biopsied? We are using partner sperm? Donor 257? We could explain to you what to expect on cycle day 0, 1, 3, and 5-7. You could ask us questions. I am hopeful we will go back to that again one day, when it is safe for everyone.

When you get wheeled into the operating room, we do a “time out” through the tiny window that leads to our sterile lab- we confirm your name and date of birth and IVF cycle plan with the physician. Then you will start to go under, as the anesthesiologist puts you “to sleep”. After you are comfortably asleep, the nurses, medical assistants and physician will drape all of your exposed skin with soft sterile towels, so that your human dignity is preserved while you are asleep, and only a small square of your body directly in front of the physician is exposed. Then the vagina is washed and prepped for the ultrasound guided transvaginal oocyte retrieval. The physician positions the gooseneck light, the OR lights are turned down low. And then the retrieval begins!

So what is the egg retrieval like from the embryologist’s perspective?

The Egg Retrieval

The egg retrieval is often the first patient procedure we learn as junior embryologists. Getting “signed off” on retrievals is a HUGE moment for our clinical career. Even after years and years of doing retrievals, they are still exciting for me. It is my job to hunt for every single egg. No matter how obscured by blood, mucus, or epithelial cells they are. No matter how misshapen, dark, abnormal or odd the eggs are (see images below of unusual eggs!). We depend on eggs being surrounded by a nice “cloud” of fluffy, nurturing cumulus cells. But sometimes the stimulation does not go as planned. The cumulus cells are a small tight dark ball. Sometimes they are shot through with capillaries. Sometimes eggs get ripped out of their cumulus cells entirely by the suction of the needle. And it doesn’t matter, we have to find them all.

In general, we know how many eggs to expect. We want to know the number of follicles over 14 mm- that gives us an indication of how many mature eggs will be retrieved. and we want to know the number of “small” follicles too- how many may not be holding a mature egg.

As the tubes of follicular fluid are handed through the window, we take them into a dark, warm, and humid environment. Then, we pour the fluid into a petri dish and start examining it closely under a microscope. As I find eggs, I call to your clinical team; One, Two, Three, and so on, so everyone knows what I’m seeing. Everyone is waiting for the embryologist to find and call the first egg. There is nothing worse than not finding eggs. Sometimes, one tube will go by, then another, than another and still no EGG! That is when I always call in a second set of eyes to double check my work. Usually, by the 5th or 6th tube at the latest, eggs are found. But occasionally, we have a retrieval that yields no eggs. Something went wrong with the stim. Maybe only one egg was expected, but it can’t be found. Maybe the patient didn’t time the trigger correctly or the surgery started late and the patient ovulated. Maybe the trigger didn’t “absorb” properly. Maybe it’s a rare case of empty follicle syndrome. Whatever the cause, “no egg” retrievals are devastating. For the patient first and foremost, but your embryologist care team feels it too.

At the same time as your retrieval is happening, the sperm for your egg insemination is being processed. Maybe it is being thawed, or in the case of fresh samples, it is being separated from the semen of the ejaculate and being prepared so the best most “motile” sperm will be available for later use.

Post Egg Retrieval

Mostly, we get the number of eggs we expect, based on the number of large follicles seen by follicle ultrasound. Occasionally, we get a huge surprise and get more eggs than expected! After the eggs are collected they are washed, and sometimes we let them rest in the cumulus cells in an incubator hoping for any last – or slow maturation to happen, before we process them further. In conventional IVF the eggs stay in the cumulus until they are combined with sperm cells. But if ICSI will be performed, then we “strip” them of the cumulus cells, grade them, and asses the quality. On average, about 80% of the eggs that are retrieved will be mature enough to fertilize. To asses egg maturity and quality we essentially dissolve the cumulus cells from around the eggs with an enzyme (the same one found in nature in the sperm head!). Then we gently swish each egg cell up and down in a tiny pipette, about the width of a sharp pencil lead. In the end we only want to see one single, clean cell- THE EGG!

Then, we grade the maturity and separate them for fertilization. We want to see mature MII oocytes. Mature eggs are referred to as “MII” ie. “meiosis two” ready oocytes. The final meiotic division– where the egg’s chromosomes are split in half one final time, will not happen until the egg is injected via ICSI, or one sperm breaches the “zona pellucida” in conventional IVF.

Besides seeing nice mature MII oocytes, we may see slightly immature eggs, called MI (Meiosis I) or very immature eggs called “GV” (ie geminal vessicle). Unfortunately, sometimes we see eggs that have fractured zonas, or are severely compromised due to vacuoles, dented cyctoplasm, or other abnormalities. I have included several images of abnormal eggs below!


Whether you and your physician opt for ICSI or conventional IVF, or if your lab only offers ICSI, your eggs will be combined with your partner or donor sperm in the afternoon of the day of the egg retrieval. This is referred to as “insemination” and it is not the same as fertilization. I will talk about ICSI, what it is and why I love it, in another Embryologist Perspective post!

Just because we put egg cells and sperm cells together doesn’t mean they will fertilize… stay tuned for the next Embryologist Perspective post on Day 1- The Fertilization Check!!

Oocyte retrieval- Technical Notes

Oocyte retrieval is a particularly sensitive procedure and special attention should be given to temperature and pH as well as efficient and quick handling.

ESHRE Guideline Group on good practice in IVF labs , December 2015

  1. An identity check before the oocyte retrieval is mandatory.
  2. The time between oocyte retrieval and culture of washed oocytes should be minimal.
  3. Prolonged oocyte exposure to follicular fluid is not recommended.
  4. Appropriate equipment must be in place to maintain oocytes close to 37°C. Flushing medium, collection tubes and dishes for identifying oocytes should be pre-warmed.
  5. Follicular aspirates should be checked for the presence of oocytes using a stereomicroscope and heated stage, usually at 8-60x magnification.
  6. Exposure of oocytes to light should be minimized.
  7. Timing of retrieval, number of collected oocytes and the operator should be documented.

Additional Embryologist Perspectives

An immature GV oocyte with abnormal, jagged cytoplasm.
An egg that appears to be “two cells” either an abnormally large polar body, or a “parthenogenic” activation leading to an abnormal cell division. An empty zona with no egg inside.
An abnormally small egg with a baggy zona around it. an “ooplasm” ei, an egg cell with no zona pellucida.
Dark abnormal inclusions.
A smooth endoplasmic reticulum visible in an oocyte.
Some sort of sharp looking mineral or crystal like inclusion in an MI oocyte.
Some sort of sharp looking mineral or crystal like inclusion in an MII oocyte.
An abnormal zona pellucida and abnormally large polar body with cell fragments in the perivitelline space.