Oocyte or egg retrieval is the procedure
marking the beginning of the second significant phase of an IVF cycle. At this
point, the focus of care shifts from inside the body (in vivo)
where the patient’s ovaries have been stimulated by fertility medications to
produce many eggs, to the laboratory (in
vitro) where the eggs are carefully handled in preparation for in
vitro fertilization, IVF.
Egg retrieval occurs 34.5 to 39 hours after hCG is administered by injection
to trigger the final stages of egg maturation and to release the eggs from the
wall of the follicle. Once they are floating free in the follicular fluid,
they are ready for retrieval. The procedure usually takes less than 20
minutes, with a recovery period of approximately an hour.
While the patient is under mild sedation, a physician uses a transvaginal ultrasound
probe to visualize the follicles. The probe also is outfitted with a needle to
puncture and aspirate the tiny sacs. The fluid containing the egg is aspirated
into multiple tubes that are passed to the embryologist who empties the
contents into a petri dish to begin the search for the eggs. Once located,
they are removed from the mixture of follicular fluid and blood and placed
into a culture medium designed in temperature and chemical composition to
resemble the environment inside the body.
The culture dishes containing the eggs are then placed in an incubator, set at
body temperature, for several more hours to complete the ripening (maturation)
process. The timing of these events correlate to those that occur naturally
and the egg retrieval is performed shortly before ovulation
would normally occur. After the period of in vitro maturation, the oocytes are
placed in drops of culture medium that contain processed sperm. (Sperm are
prepared for IVF by isolating motile sperm from other elements of the semen).
If fertilization occurs, it happens during the next few hours. The embryos
continue to develop over the course of the next three to five days. On the day
of transfer, our embryologists select
the healthiest embryos for return to the uterus during the embryo
transfer procedure.
In some cases, other laboratory-based techniques are required following egg
retrieval. Fertilization may be assisted by intracytoplasmic
sperm injection (ICSI), a micromanipulation procedure that involves
injecting a sperm directly into the core of an egg. Techniques such as embryo
co-culture and assisted
hatching may be used to help in embryo development. In some cases, preimplantation
genetic diagnosis (PGD) may be performed on developing embryos to identify
certain genetic abnormalities and prevent the transfer of affected embryos
during an IVF cycle.
