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Embryology Lab Tour

The Embryology lab at the Loma Linda University Center for Fertility and IVF is responsible for identifying and processing patient oocytes for fertilization, embryo culture and selection for transfer back to the patient, cryopreservation and storage of extra embryos. In addition, the lab also processes embryo biopsies and submits them for preimplantation genetic diagnosis (PGD).

Unique services include: (1)  the application of Embryo Glue to assist embryo implantation during the transfer step (2) Day 5 blastocyst transfer to select for optimal embryos for transfer (3) individualized incubator chambers for separate patients (4) availability of an acupuncture-assisted embryo transfer procedure and (5) the latest in the vitrification procedure to freeze embryos for storage.

  Oocyte Retrieval

Under ultrasound guidance, the patient oocytes or eggs are removed from the ovaries and placed into pre-warmed culture tubes. The oocytes are bathed in a mixture of follicular fluid and culture medium and must be identified in the lab.

  Oocyte Identification

The oocytes are identifed using a dissecting microscope and categorized as mature, immature or atretic (dying). Each oocyte is washed clean of cellular debris and incubated in a separate tissue culture well containing culture medium rich in nutrients.

   Oocyte Insemination

The mature oocyte is ready to be inseminated with washed sperm cells (conventional IVF) or injected with a single sperm (ICSI, intrcytoplasmic sperm injection). Before this can take place, the layers of cumulus cells surrounding each oocyte has to be removed to facilitate the procedure. The cumulus removal process is performed using another microscope with a warm stage.


The oocyte is held in place by a large pipet that has a gentle suction pressure. A fine needle pipet containing a single sperm is injected inside the oocyte. The oocyte is released and placed back into the tissue culture well with culture medium. The next step is to incubate all the injected oocytes overnight in their special incubators.


The next day following oocyte retrieval, each oocyte is examined for signs of fertilization under the inverted microscope. This is usually the presence of 2 pronuclei near the center of the oocyte (arrow). Unfertilized oocytes do not have any pronuclei present. The physician and patient are informed of the number of fertilized oocytes. The fertilized oocytes are incubated for another day and re-examined for development.

  8 Cell Embryo

The faster developing embryo reaches the 8-cell stage as shown in this photo. This is usually a good sign of developmental potential and the embryologist records all the observations made on this day. Not all the individual cells look round and even, they may be larger or smaller in size. As long as a few of the cells are normal, the embryo has a good developmental potential.


When the patient desires the PGD procedure to get more information about the health of each embryo, 2 of the cells are removed from each 8-cell embryo using a large pipet. The extracted cells are processed and sent to a diagnostic lab for analysis. The patient obtains the results in less than 24 hours after the embryo biopsy procedure.

 Blastocyst-Day 5 Embryo

Five days after oocyte retrieval, the embryo has grown to the blastocyst stage. The best shaped blastocysts are selected for embryo transfer. Some selection criteria include the appearance of expansion of the blastocyst, the presence of an inner fluid-filled space called the blastocele, the tightness of the cell layers and the thickness of the zona pellucida or egg shell. The remaining unused embryos are frozen and stored in accordance with the wishes of the patient.

  Ready for Transfer

The embryos are loaded into a plastic embryo transfer tube or catheter. The physician then guides the end of the catheter into the patient's uterus throiugh the cervical canal under ultrasound guidance. The embryos are gently injected into the uterus and the catheter is removed. The patient is encouraged to rest for a few minutes and is given further instructions after the embryo transfer. The pregnancy test is done 2 weeks after the transfer procedure and involves giving a blood sample.

This concludes a quick tour of the Embryology lab procedures. We hope that this has been informative. If you have questions on this or other sections of the fertility center, web site, please contact us.