Collecting Eggs and Embryo Development

The nest stage after egg production is egg retrieval. We use I.V. sedation at retrieval, and therefore we tell our patients not to eat or drink anything after midnight the day before retrieval. Our anesthesiologists are appropriately reluctant to give patients sedation if they have a full stomach. We make a few other recommendations as well: We recommend that you not wear perfume to the procedure room, as we do not know what effect perfumes may have on the air environment inside the embryology lab.

The morning of the retrieval is usually one of great anticipation and more than a little nervousness. Almost uniformly patients apologize for being nervous and almost uniformly and assure them that we would be more worried about them if they were calmer. After all, a lot of time, effort and money has gone into bringing you to this point.

Patients have also had more control up to this point. They’ve done the injections themselves, come in for the blood work and the ultrasounds and been able to pretty much keep track of what’s been going on. From the retrieval on however matters are pretty much in our and in nature’s hands. Nobody likes giving up all control, and it’s understandable and appropriate that this new phase of the cycle brings its own new set of anxieties.

We meet with the patient before the procedure, answer any questions, and then give them a chance to speak to the anaesthesiologist. We walk together to the procedure room. In the procedure room, there are usually the following people: the patient, his scrub nurse, a circulating nurse, the anesthesiologist, and the Doctor, as well as an embryologist who walks in to further identify the patient. We make a major point of identifying and re-identifying our patients through the process, because we like our patients and their families to be as comfortable as possible that everything imaginable is being done to insure that their sperm and their embryos end up in their own bodies. We even go so far as to have the patient identify her own name etched into the Petri dishes that we use in the laboratory during her case.

After entering the procedure room, the patient lies down and the anesthesiologist starts an I.V. Personally, we like to position the patient while she’s awake to insure that we don’t place her into an awkward position that might cause aches or pains later on. We use an intravenous sedation to insure that we prevent discomfort during the retrieval. This is not general anesthesia and usually results in a much more comfortable awakening shortly after the procedure is done.

After anesthesia is started, the egg retrieval is performed by inserting the ultrasound probe into the vagina. The probe, unlike during the morning ultrasounds, is fitted with a needle guide through which we can insert a long needle that pierces the back wall of the vagina and gets pushed into the ovary. Nature was kind to us when it came to egg retrieval. The ovary is right behind the wall of the vagina and it is usually a fairly straightforward process placing the needle, under direct division, into the ovary and in and out of each follicle. We can then drain the follicles and catch the fluid, which the circulating nurse delivers to the embryologist on just the other side of the wall. The embryologist then goes ahead and identifies each one of the eggs. We do one ovary at a time, often pausing between ovaries to allow the embryologist to catch up.

The eggs usually arrive into the laboratory attached to what looks like a netting or web. These are the cumulus cells that surround the egg inside the follicle. Shortly after retrieval these cells are separated from the egg as the egg is prepared for fertilization.

How many eggs should we expect? In general, we usually retrieve within 10% or 15% of the number of follicles that were seen on the ultrasound. Of course as the number of follicles rises, the accuracy by which we can predict the number of eggs we’ll retrieve drops. There are several reasons for this. For one, as the number of follicles increases, the percentage that won’t be optimally matured increases as well. Many non-optimally matured follicles will not have mature egg in them. Second, as we identify more and follicles, it’s easier to miss a follicle on ultrasound. Sometimes when we drain one follicle during the retrieval, we’re surprised to see another follicle right behind it that we had originally missed.

We usually counsel patients not to put too much importance into the number of eggs that we actually retrieve. Once we get beyond a small number, usually four or five, the absolute pregnancy rate does not seem to be very much affected by the number of eggs. We counsel them not to worry that the person in the recovery room bed next to them may have a much larger number. More is not always better. In fact, some of the highest numbers we retrieve (as in patients with polycystic ovaries) often contain very large numbers of immature eggs and will not result in better, or more high-quality embryos.

The retrieval usually lasts about 20 minutes. Afterwards, we wheel the patient on a stretcher into a recovery room where recovery is usually quite rapid. Different people will have different symptoms after retrieval. Some will feel very much like themselves very quickly. Others might feel sore or woozy from the anaesthesia for a longer time. A good rule of thumb is that if you don’t feel 80-90% normal by 24 hours after the egg retrieval, it’s a good idea to give us a call. It’s not uncommon to have a little bit of bleeding after the retrieval, but bleeding more than a period-type bleeding should be bought to our attention. In general, trust your gut instincts. If you have a symptom that you want to run by us, go ahead and give us a call. We would rather reassure you, than have you not tell us about something that could be potentially serious.

Exposure to Sperm for Embryo Development

On the day of the egg retrieval, exposure to sperm, either through placing the egg and sperm in close proximity or through intracytoplasmic sperm injection occurs. By the next morning we can tell which eggs have activated and started to divide. Many people don’t realize that injecting sperm into an egg with ICSI, which does not necessarily mean that fertilization has occurred. Fertilization involves both the entry of the sperm into the egg and the initiation of cell division. One of the first things we see is the extrusion of a polar body, sort of a mini-egg with chromosomes inside it that signals both maturity of the egg and, when the second polar body is extruded, indicates fertilization.

Depending on the particular cycle and what is planned, different techniques are used over the next few days. There are various fluid media that can be used to incubate the embryos. Different media are used for transfers that are planned for the third day, then for the fifth day, for example.

Coculture to Aid Embryo Development

There is also a technique called coculture that is used for patients that may have had previously poor development in prior IVF cycles. Coculture is a technique where viable cells from the patient’s own uterine lining or from the reproductive cells of the reproductive tracts of certain animals most commonly cows are added to the incubation fluid of the embryos. It’s believed that this better simulates the environment inside the body where embryos normally develop. The exact mechanism by which coculture helps embryos develop is unknown. Perhaps the cells secrete a factor that improves development. Perhaps the cells absorb a toxic factor that the embryos themselves may make as they develop. Regardless of the mechanism, it appears the coculture helps about a third of the cases where development was poor before that.

Why not do coculture on every case? Unfortunately coculture is a very time and labor intensive procedure. It can add several thousand dollars to the cost of the cycle and, depending on where the cells are obtained, can add an additional month to the length of the IVF procedure. For these reasons, coculture is reserved for those cases where we really think it will make a difference.