An egg retrieval (also known as an ovum pickup or OPU) is a procedure that aspirates (suctions out) fluid and eggs from the ovarian follicles. A typical egg retrieval procedure takes about 15-20 minutes to complete and is usually performed under sedation.
An egg retrieval is scheduled for 35-36 hours after you administer your trigger medication. This means that you have already administered all of your IVF stimulation medications and are nearing ovulation. It’s important to administer your trigger medication exactly as instructed to ensure that your eggs have optimal time to mature and ovulation does not occur too early.
Almost all egg retrievals are performed under an IV sedation (such as propofol). Therefore, you should not feel any pain or discomfort during the procedure. There is little to no risk associated with IV sedation, though an anesthesia consult may be required if you have never received anesthesia before. In rare instances, there is a risk of an allergic reaction, decreased respiratory function, and infection at the medication injection site. You are monitored by an anesthesiologist throughout the entire procedure.
Once the sedative has been administered and you are comfortable, the physician will use the vaginal ultrasound probe to view the follicles in the ovaries. The physician will then guide the needle through the vaginal wall, into the ovaries, and into each follicle using the ultrasound as a guide. Once the needle is inside a follicle, the follicular fluid (and hopefully an egg) is aspirated through the needle and catheter and into a sterile tube. The follicles can also be flushed out with a washing fluid if needed. The physician does this for each follicle in both ovaries. Once a tube fills up with fluid, it is taken to the IVF lab and is replaced with an empty sterile tube.
In the IVF lab, two events occur:
1. The embryologist searches through all of the fluid for eggs. Any eggs that are found are isolated in a separate dish and the extra fluid is discarded.
2. The eggs are cleaned. Most eggs have a lot of cumulus cells around them (residual cells from the follicles, see photo), which are removed to help with the counting and grading of the eggs. Note: the eggs are only graded for ICSI or egg freezing, but not for conventional insemination.
Once all of the follicles have been aspirated, the physician will remove the needle and ultrasound probe, and the embryologist will indicate how many eggs were retrieved. The anesthesiologist will discontinue your sedation and you will be placed in a recovery area for ~45 minutes. While recovering, your vital signs will consistently be monitored, and you should be informed of your next steps, restrictions, and final egg count before you leave the clinic.
You can expect to feel some abdominal discomfort and cramping after your egg retrieval, so you are encouraged to rest for the remainder of the day. Driving is not recommended following sedation, so please have someone available to drive you home. Bloating, mild constipation, and some spotting are normal after an egg retrieval, but please let your care team know if you experience any shortness of breath, nausea/vomiting, and/or rapid weight gain as soon as possible, as these can be signs of OHSS (ovarian hyper-stimulation syndrome).
Overall, the egg retrieval procedure is a routine, low-risk procedure. If your eggs are being inseminated, you will receive a call the following day with an update on how many of your eggs fertilized. If your eggs are being frozen, they will be frozen shortly after the egg retrieval procedure.
Why aren’t all retrieved eggs able to be frozen or inseminated?
It can be frustrating to discover that only a portion of your retrieved eggs are mature enough to be inseminated or frozen. An embryologist determines an egg’s maturity by the presence of a polar body, which means that the egg is mature enough to be properly fertilized.
Here are all of the types of eggs that can be retrieved:
A mature egg (known as an MII or M2): these eggs have polar bodies and can be inseminated.
An immature egg (known as an MI or M1): these eggs do not have polar bodies. These eggs are given some time to mature in the laboratory, but they are only inseminated if they mature in that time.
A germinal vesicle (known as a GV): these are very immature eggs that have a circle with a dot inside of them (see picture). GVs are not inseminated due to their immaturity.
An atretic (degenerate) egg: these eggs are nonviable and are not inseminated.
An abnormal egg: these eggs may consist of 2+ cells, or they may be giant cells (meaning that proper cell division did not occur and they have too much DNA in them), or they may have a lot of vacuoles (cavities) in them. These eggs are not inseminated due to their abnormalities.
A fractured egg: these are seen as empty zonas (the shells that surround the egg). This can occur if a zona is abnormally fragile, or if the zona is broken during the retrieval process. These cannot be inseminated.
In most cases, roughly 70% of the retrieved eggs are able to be inseminated. If you have a significantly lower percentage of mature eggs, this could indicate any of the following:
An egg quality issue: your eggs did not mature the way they were supposed to based on the sizes of your follicles.
A medication issue: your eggs did not respond to the IVF stimulation medications correctly.
An underlying issue: this could be a hormonal issue, such as PCOS, or some unknown issue that caused less eggs to mature than normal.
What makes an egg mature?
Eggs go through a process known as meiosis as they mature. Meiosis involves a series of 2 cell divisions (meiosis I and II). During fetal development (before the woman is born), millions of eggs are created inside a woman’s ovaries. This means that women are born with all of the eggs that they will ever have. All of these eggs sit inside sacs (called primordial follicles) in the fetal ovaries. These eggs begin their first cell division (meiosis I), but the process halts pretty quickly. And thus, the eggs (called primary oocytes) sit inside of their primordial follicles in the ovaries, arrested in meiosis I, for many years.
Fast forward to when puberty begins. At this point, women normally get their menstrual cycles each month, during which time one egg is released from its follicle in the ovary through a process known as ovulation.
Each cycle, some eggs (primary oocytes) resume the process of meiosis I that was halted for many years. As this occurs, the follicles surrounding these eggs also begin to grow. But only one egg ultimately matures each cycle, which is the egg that will be ovulated. The other eggs that began maturing will all degenerate.
This "chosen" egg ultimately completes meiosis I. At this point, it divides into 2 cells: an egg and a small polar body. The polar body is nonviable and will eventually degenerate.
The egg then begins the process of meiosis II (the second cell division), but it halts its development right after it begins meiosis II. This (now mature) egg sits inside its large follicle (now known as a Graafian or dominant follicle) until ovulation occurs.
After ovulation occurs, the egg (and its polar body) is released into the Fallopian tube. If fertilization occurs, the egg (and polar body) will complete meiosis II. When the egg completes meiosis II, it creates a second polar body, which is nonviable and will degenerate. The polar body that was ovulated with the egg may also divide into 2 polar bodies, but these also degenerate.