Jill Carrozza, Senior Embryologist @ Carolina Conceptions

“The Lab” in an IVF clinic is often the forgotten entity of the entire IVF process, but without the lab an IVF clinic just could not function!  From the time you walk through our doors, you are greeted with a great administrative and financial staff, medical assistants, nurses and doctors, but unfortunately you often never get to meet the embryologists.  So in turn, many questions can arise on exactly how our IVF lab functions, especially what happens to your eggs and sperm after they are collected. This is the job of “the lab.”

After months of medications, shots, and doctor visits, you (our patient), finally administers the HCG trigger; 36 hours later you arrive to our facility for your “Egg Retrieval”.  The day prior to your retrieval, the lab is busy carving dishes, making media, filling out appropriate paperwork, and finding an IVF Proces timelineincubator for your embryos for the next 6 days.  This is done for each and every individual patient who has an egg retrieval.  Once your retrieval is done and we’ve collected your eggs, they are pooled together, placed in dishes and an incubator labeled with your full name and medical record number. While you are having this procedure done, the sperm is being prepped in our Andrology lab.  Just like the eggs,  sperm is similarly labeled with your information.  Around 2-3 hours post retrieval, the lab will then “strip” your eggs. Each egg has cumulus cells around it. These cells can be seen by the naked eye and resemble puffy clouds.  These cells are “stripped” or broken down to expose the egg itself to assess the maturity of the egg.  Mature eggs (an egg with a polar body) are pooled together for ICSI (Intracytoplasmic Sperm Injection), the immature eggs (an egg with no polar body or a germinal vesicle) are pooled together and discarded after ICSI.  Around 1-2 hours post “stripping”, ICSI is performed.  This process is where we inject one sperm into each egg.  All the injected eggs are then placed in their assigned dishes and incubators.  They will remain in this assigned incubator until the final assessment of each embryo on day 6.

IVF lab

Immature Vs. Mature Egg


ICSI: Intracellular Sperm Injection







The Lab assesses your embryos on various days: Day 1 (Fertilization check), Day 3 (Cleavage stage), and Day 5 and 6 (Blastocyst stage).  On Day 1, we look for embryos with 2 polar bodies and 2 pronuclei. Day 3, we like to see the embryos between the 6-8 cell stage.

IVF Lab Fertilization check

Day 1: Fertilization Check

IVF embryos

Day 3: Cleavage Stage








Day 5/6: Blastocyst Stage

Day 5/6: Blastocyst Stage


Day 5 and 6, we look for expanded or hatching blastocysts with defined ICMs (Inner cell mass: extremely important, these cells produce the baby) and cobblestone shaped trophectoblasts (these cells produce the placenta).  An embryologist will update you by phone on the development of your embryos on each of these days.




Here at Carolina Conceptions we typically perform day 5 transfers on most of our patients, however since every patient and embryo is different, some of you may have a day 3 or day 6 transfer.  Please understand many factors need to be considered in this process.  Our doctors and embryologists want you to be successful and will decide whether a day 3, day 5 or day 6 embryo transfer is the best approach to IVF labachieve a pregnancy.  Also at this time, PGD/PGS (Pre-implantation genetic disorder/Pre-implantation genetic screening) would be performed on your embryos if this was in your stimulation plan.  PGD/PGS is a process where a few cells are expelled from a blastocyst on day 5/6 and sent to a genetic testing company for DNA processing.  These companies test for various genetic abnormalities in an embryo and can be very useful for some patients.  Please be advised, not all the embryos will be sent out for testing. The blastocysts need to be adequately expanded with defined ICMs (inner cell mass) and evenly shaped trophectoblasts. After biopsy, the embryos are then frozen.  The biopsied cells are sent to the genetic lab. Once we receive the genetic testing results and if there are “normal” embryos then an FET (Frozen Embryo Transfer) would be the next step.

As for freezing embryos, we have a strict freeze criteria here at Carolina Conceptions and only the top quality blastocysts will be frozen on day 5 and/or day 6.  Let me reiterate, every patient and embryo is different, some of you may have embryos to freeze while others may not.  The embryos we freeze are IVF labstored in cryotanks in the laboratory.  These tanks have multiple chambers and can hold 5-6 cryostraws on a long “cane.” Up to 540 straws are stored in each tank.   Embryos, when in constant contact with liquid nitrogen, can last indefinitely.  This can also be said for frozen sperm.  We fill the tanks weekly with additional liquid nitrogen. So please have no worries. We are taking care of your frozen embryos and sperm.

We hope this gives you better insight as to what goes on in the lab.  We understand it can be a very stressful and emotionally draining time. The embryologists will always stay in contact and update you with all and any new information concerning your embryos. We very much hope you will have success!