Lab FAQs

How can I be sure that the IVF laboratory will not mix up any of my sperm, eggs or embryos with those from another patient?

An error of this type has never happened in the IVF laboratory at Pacific Fertility Center. This is because we take special precautions and extra care in following SurTransferTM protocols and double check every step of each procedure. Petri dishes and test tubes containing sperm, eggs or embryos are labeled with duplicate identifying information for each patient and color coded to prevent mix-ups. If we receive a sperm sample from John Smith, for example, his ID will be checked when he gives us the sample and he will be assigned a color (red, for example). Any tubes or dishes that are used in the processing of the sample will contain his full name and his partner's full name, another piece of identifying information such as date of birth or social security number, and will be color coded in red. In addition to these labeling procedures, there is a cross-checking system to prevent human errors. Each time a procedure is performed by an Embryologist, a second Embryologist has to witness the event before they are released to a Physician. If the sperm are being used to inseminate his partner's eggs, a second Embryologist verifies that the correct eggs and sperm have been removed from the incubator before the Embryologist performing the procedure can actually proceed with the insemination of the eggs. At the conclusion of the procedure, both Embryologists sign the patient's chart, which is the legal record of the procedure. These same checks and balances are used during each laboratory procedure and can be seen in action by patients having embryo transfers. At transfer time, the Embryologist performing the transfer will ask the patient their full name and date of birth, and repeat the name and date of birth back to the patient to verify what they heard. A photograph of the embryos being transferred is taken with the patients name imprinted on the photograph. The identity of the dish containing the embryos is double checked by a second Embryologist and the embryos are loaded into the transfer catheter. As the catheter is handed over to the Physician, the Embryologist will repeat the patient's name and give details of the contents of the catheter (e.g. "here are 2 embryos for Joyce and John Smith.") The photograph of the embryos is given to the patient and a copy is kept in the medical record.

This “double key” system with two embryologists is why we think it is important to do IVF in a lab that has at least two embryologists on duty at all times, including weekends.

Surplus embryos being frozen after a transfer are catalogued with full name, ID (date of birth or social security number) date of freezing and details of the embryos being frozen. Embryos are frozen inside special straws and in addition to careful labeling, color-coding is also used as an added precaution. As with other procedures, a second member of the laboratory staff has to witness the procedure and verify patient and embryo details for any freezing or thawing event.

As with any laboratory procedures, we welcome questions on this subject and would be happy to discuss this topic further.

Can you tell the sex of my embryos?

Yes. It is possible to determine the sex of an embryo by performing a procedure called Preimplantation Genetic Screening (PGS). This involves drilling a small hole in the shell surrounding the embryo and removing one or more cells. The cell can then be screened in a genetic laboratory to determine if it contains two X chromosomes (female) or one X and one Y chromosome (male). This testing can also determine the correct chromosome number for all 24 chromosomes. There are some advantages and some disadvantages to this testing so we recommend consultation with one of our physicians and our consulting genetic counselor if you think you may be interested in this option. 

I've heard that having embryos transferred at the blastocyst stage gives really high pregnancy rates. Shouldn't every IVF patient have this procedure?

Embryos that have grown successfully in the laboratory for 5 or 6 days are called blastocysts. They have gone beyond the stages where it was possible to count the number of cells that they contain and have begun to differentiate into 2 different cell types. A normal blastocyst should have developed by day 5 or day 6 after egg retrieval and the outer cells (trophectoderm) and inner cells (inner cell mass) should be clearly visible. These cells give rise to the placenta and fetus respectively. Since the blastocyst now has the first placenta cells, it is ready to hatch from its shell and implant in the uterus.

On average, about 53% of fertilized eggs will develop to the blastocyst stage. This number will be lower in older patients, and higher in young patients. Younger patients tend to have more eggs and therefore embryos, which will give them a greater chance of having some embryos that develop into blastocysts. The main advantage of keeping the embryos to day 5 in the laboratory is that we are able to select those embryos most likely to successfully create a viable pregnancy. If the desired number of embryos for transfer is achieved by day 3 (for example, there are only 2 or 3 good embryos on Day 3), there may be no particular advantage to keeping them in the lab any longer and they should go ahead and be transferred back to the patient on Day 3. 

Can you freeze eggs?

To survive freezing, a cell needs to be dehydrated, since water expands as it turns to ice and would burst the cell. We replace the water in the cell with an antifreeze or cryoprotectant. Our ability to freeze cells (cryobiology) depends on being able to quickly replace the cell water with cryoprotectant and works well in free living cells such as sperm and embryos. Large groups of cells (tissues) cannot be frozen, as difficulties exist in getting the water out of the cells at the center of the tissue. Some success has been reported with freezing ovaries, but only when the tissue was cut into tiny pieces or strips, since this allows for good penetration of cryoprotectant to all cells.

Eggs present their own unique challenges to cryobiologists because in theory, they should freeze easily, but in practice they have resisted freezing for over 2 decades. An egg is a single free-living cell and it can be dehydrated quickly. However, when the egg is released from the ovary, it is in a very critical phase of development that is very vulnerable to the freezing process. Since the egg is preparing to welcome a sperm, the DNA (or chromosomes) within the egg is in a very delicate phase of reorganization. The egg is in the process of getting rid of half of its DNA, a process that is not completed until after the sperm has entered the egg. Early attempts to freeze eggs fatally disrupted the DNA reduction process and left the majority of eggs non-viable after thawing. In recent years however, an alternative freezing method has been employed with great success for eggs.

Vitrification is an ultra-rapid freezing method that has been employed since 2006 to successfully preserve eggs. Eggs are exposed to higher concentrations of cryoprotectants that would be used in the older slow freezing methodology, and they are then loaded into tiny straws and frozen at high rates (over 5,000°C/minute). The whole process is relatively fast and avoids the critical problem of ice formation by combining fast freezing with high concentrations of cryoprotectants. It’s also fast enough to prevent serious damage to the DNA restructuring process allowing eggs to be thawed and fertilized successfully at a future date. Click here for more information on vitrification.

How are embryos frozen?

Embryos can be frozen at different times after fertilization. Most typically, embryos are frozen 5 or 6 days after the sperm and egg were combined, but they can also be frozen immediately after fertilization (day 1) or any day thereafter. Freezing is a stressful process for an embryo, and only embryos that are growing well in the laboratory will tolerate the freezing procedure.

Before an embryo can be frozen, all the water that it contains must be removed. Since water expands in size as it turns to ice, water inside the embryo would burst (kill) the embryo if we simply placed it in the freezer.

To prevent the embryo from shriveling as the water is extracted, we replace the water with an antifreeze (or cryoprotectant). Antifreeze is a solution that does not expand in size when it freezes. The embryo is cooled to room temperature as the water is replaced with antifreeze.

The water is removed from the embryo in 2 stages using a weak and then a strong cryoprotectant solution. When most of the water has been removed the embryo is inserted into a tiny straw, and plunged into liquid nitrogen at a temperature of -196°C.  This ultra-rapid cooling process is called vitrification and embryos tolerate the procedure very well. Over 90% of all embryos vitrified survive the process and are available for transfer in as little as 20 minutes after being warmed out of the freezer.  

How are frozen embryos stored and monitored?

The air that we breathe contains a gas called nitrogen. This gas makes up about 78% of the air around us. If nitrogen gas is cooled, it becomes a liquid at –196°C. This liquid is very stable and easy to work with, and its stability makes it a good medium for storing frozen cells or tissues.  In the laboratory we have large tanks filled with liquid nitrogen in which we store frozen embryos. Each tank, actually called a DEWAR, is in many ways like a large thermos flask. It is vacuum lined and has a heavy lid to slow the evaporation of the nitrogen. Each patient has a designated storage space within a tank, where their eggs or embryos are kept. The straws that contain the embryos are labeled with precise and unique identifying information. At a minimum, this information includes the patients full name, their date of birth or their social security number, the number of eggs or embryos in the straw, the stage at which the embryos were frozen and the date on which the freezing was performed.

The tanks that contain frozen eggs and embryos are monitored 7 days a week, 365 days a year. Each tank gets a physical inspection each day, looking for problems or signs of wear. The quantity of nitrogen in the tank is assessed as a means of monitoring for a possible slow leak or an impending tank failure. The nitrogen in the tank is topped off daily since it continuously evaporates at a slow rate (if a tank was not filled regularly, the nitrogen would evaporate entirely in about 1 week).

Electronic tank monitoring uses different sensors to ensure that tanks perform to specifications. A probe attached to the tank lid, actually sits in the nitrogen with the embryos. The probe will detect a rise in temperature within the tank, or a drop in the level of liquid in the tank. All of these sensors are connected to a telephone system that will alert staff to an alarm condition, if one happens out of hours.

The telephone alert system is a monitoring device that monitors each individual piece of critical equipment in the laboratory. It requires that embryologists be contactable at any given time, and calls and recalls each person in turn until somebody enters the laboratory and cancels the alarm. The alarm calls our cell phones and we try to have an embryologist be in the laboratory within about 30 minutes (day or night) after the alarm is set off. The alarm system is tested weekly and continues to run on battery power in the event of a power failure. The alarm system can also be checked remotely. The status of each individual tank can be ascertained by telephone at any time. 

How long can embryos be stored?

No one knows what the maximum storage period might be. Procedures for human embryo freezing were developed in 1984 and only went into widespread use in the late 1980's. This means that the longest time a human embryo has been stored is 20-30 years, and typically, patients that have left embryos in storage for this long are not coming back for them. Some patients have come back after 10-15 years and the embryos have been thawed successfully. Beyond this time frame, since we don’t have a lot of data, we don't know how long an embryo will remain viable. In theory however, cryobiologists believe that embryos can be stored indefinitely with no loss of viability.

How are embryos thawed?

Thawing the embryos is simply a reversal of the freezing procedure.

When an embryologist removes embryos from the freezer, a second embryologist is required to witness the act, and verify the identity of the embryos before they can be thawed. Under no circumstances can a lone embryologist remove embryos from the freezer.

The embryos coming out of the freezer (at –196°C) are warmed to room temperature in 3 seconds. This rapid thaw method minimizes damage to the embryo from ice crystals that can form during warming. The embryologist has to remove the antifreeze from the embryo and replace the water that was removed at the time of freezing. This is done by incubating the embryo in decreasing concentrations of the antifreeze, and increasing concentrations of water. Over a period of 15 minutes, the embryo is stepped through 3 different solutions, until finally the antifreeze is gone and all the water has been replaced.

The thawing procedure is performed at room temperature, and once complete, the embryo is warmed up to body temperature (37°C). It can be ready for transfer in as little as 20 minutes after leaving the freezer. 

Can freezing damage my embryos?

Yes, physical damage may result to individual embryos due to the stress of freezing and thawing. The damage can arise in 2 ways. First, despite our best efforts, it is possible that ice shards will form within the vial or straw, and pierce or kill one or more cells within the embryo. Second, during thawing, water rushes back into the embryo at a faster rate than the antifreeze leaves. This causes swelling of the cells, and occasionally individual cells will not tolerate this swelling and burst.

The first baby resulting from a frozen-thawed embryo was born in Australia in 1984. The embryo had 8 cells when frozen, but 2 cells died during thawing. Even though the transferred embryo had only 6 living cells, it was still capable of developing into a normal baby.

We consider that any embryo that survives thawing with the majority of its cells intact has the potential to establish a pregnancy. In practice, over 90% of embryos survive with all their cells intact and these embryos implant at high rates after transfer. Damage to embryos tends to be an all-or-none phenomenon, that is, either the embryo survives or doesn’t. Loss of cells does not result in birth defects.

In rare cases, an embryo might not be recovered during the warming process. The straws that embryos are frozen in are extremely tiny and delicate, and occasionally they break or crack under the extreme physical forces that are created during freezing. The straws are actually warmed in a water bath when removed from the freezer, and any defect in the straw could allow water in, destroying the embryo. In practice, failure to recover an embryo happens less than 2% of the time, and we are continuously looking for ways to eliminate this side effect to the process.

Am I more likely to have a child with a genetic or congenital abnormality because I'm pregnant after a frozen embryo transfer?

Even after 20 years, there are few studies in the scientific and medical literature concerning outcomes after embryo cryopreservation. However, the few studies that have been published are thus far reassuring. Children born from frozen embryos do not seem different from children born from embryos that had not been frozen. Even if an embryo loses one or more of its cells during thawing, (see section above) this does not cause any abnormalities. Freezing does not cause or introduce genetic abnormalities. 

The only risk associated with freezing, is that the embryo might not tolerate the procedure, and could lose so many cells that it is no longer strong enough to implant and establish a pregnancy. 

What are the costs for keeping embryos in frozen storage?

The costs to Pacific Fertility Center are high. Most of the cost is accounted for by the personnel required to maintain the tanks and keep track of the embryo inventory. Embryologists receive training in handling liquid nitrogen and maintaining the frozen embryo bank. Although nitrogen liquid is relatively stable, it can cause severe frostbite, rapid suffocation and death if mishandled. We even have a special permit from the city just to have the liquid in the building and the emergency services have to be kept informed of our activities.

We buy several hundred liters of nitrogen each week to keep the tanks filled and to use for freezing of new embryos. Ask any embryologist, and they'll tell you that the real cost is in having to race to the lab at 4.00 am on a Saturday morning only to find a false alarm. Patients pay an annual storage fee to maintain their embryos in frozen storage.

Would the storage tanks survive a major earthquake or other disaster?

Probably not. While the tanks are secure and robust, they could be crushed or severely damaged by falling masonry. Any catastrophe that would collapse the building would almost certainly destroy the tanks.

The storage tanks require no power and would not be impacted by a power failure or blackout. They are made of metal and would probably survive a small or moderate fire. If the tanks were not physically damaged or knocked over in a disaster, they should survive intact. Even if no one was able to physically check the tanks, or if we were unable to obtain liquid nitrogen, the tanks should still maintain their temperature for several days. 

What are my options for using the embryos?

We hope that most couples will be able to use the embryos to have a healthy baby. Approximately one fourth of the babies delivered from assisted reproduction at Pacific Fertility Center are conceived from previously frozen embryos. Some patients undergoing frozen embryo transfer are thawing embryos after failing to become pregnant during their IVF cycle, and some are using the embryos years after a successful IVF cycle, to have a second or third child.

You may be surprised to learn that there are a significant number of people who do not want to use their frozen embryos to become pregnant. These are typically people that have completed their families and are not interested in having any more children. Having embryos remaining creates a very difficult situation for these families. The embryos can be discarded as medical waste, but the decision to destroy the embryos is not made easily. Couples with children resulting from IVF treatment often view the frozen embryos as potential children and siblings for their existing children. Coming to terms with destroying the embryos can prove difficult, and many couples avoid taking this decision by simply leaving the embryos frozen indefinitely.

Additionally, frozen embryos can also be donated for use by another couple. This can be broken down into three sub-categories: known donation, open donation and anonymous donation (see question below for details). 

What are my options with donating my embryos to another infertile couple?

It is possible to donate embryos to other couples wishing to have a child.  

There are many advantages to embryo donation, including giving another couple the chance to have a child and avoiding having to discard the embryos that took so much effort to create. However, the process resembles placement in many ways, as there are a series of requirements that need to be satisfied before the donation can be completed. The different types of embryo donation are described below.

Known donation, also called directed donation, is the donation of your embryos to a person or couple that you know personally, perhaps a good friend or family member.

Anonymous donation of your embryos means that you donate your embryos to an organization, and the organization will place your embryos with a family that you do not know and will not meet, and the identity of both the donors and the recipients will not be disclosed to either party. Through the PFC Embryo Placement Program, only anonymous embryo donations are performed, and stipulations about whom or what type of family situation the embryos are donated to cannot be accommodated (i.e.  that the embryos be donated to a two-parent household, or a household of a certain income level, or living in a certain geographic area). The placement of anonymously donated embryos operates on a first-come, first-serve basis and, at the moment, PFC has a very long list of patients wishing to receive donor embryos (currently we have nearly a two year wait).

Open donation is the donation of your embryos to a party that you do NOT know, but wish to meet, and/or possibly remain in contact with, after the embryos are donated. Open donations require further legal expertise and overall guidance and handling beyond PFC’s current abilities. For these reasons, PFC is unable to offer open donations to our patients. For those interested in an open donation, or for those requesting certain criteria be met by the recipients, patients are encouraged to research third party agencies that facilitate embryo donations, both anonymous and open. One such program is the Snowflakes Frozen Embryo Placement and Donation Program, operated by Nightlight Christian Placements. Snowflakes facilities both open & anonymous donations of embryos and can accommodate most requests from the donors and the recipients. Another possibility is Miracles Waiting, an online do-it-yourself matching program for donors and recipients. More general information about embryo donation and placement can be found at the National Embryo Donation Center (NEDC).

How are embryos destroyed when patients request disposition?

A formal request to destroy the embryos must be received in writing from the patients. The request must be signed by both partners and notarized or witnessed by a member of our staff. Once the laboratory has received the disposition notice no action is taken for 30 days. This gives the couple a cooling off period and an opportunity to change their decision.

When the 30-day waiting period has passed, our tissue bank manager and two Embryologists take responsibility for carrying out the patients' wishes. They fill out a form indicating that they have checked the disposition request and are in agreement that the patient wants the embryos discarded. They locate the embryos in the storage tank and double check the identity with the paperwork. The embryos are then removed from the liquid nitrogen tank.  Once they are removed, they will lose all viability in a matter of seconds and are disposed of as medical waste. The paperwork is complete when both embryologists sign, attesting that they performed and witnessed the destruction according to the patients' wishes. The paperwork is kept in the laboratory files and a copy filed in the medical record of the patient.