In Vitro Fertilization - Stage 2
Egg Aspiration (Oocyte Retrieval)
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Despite the continuous growth of the follicle for more than 10
days, the egg does not complete the final maturation until a
specific signal is given. This signal is given by the release of LH
from the pituitary gland in the natural cycle. This release is
blocked with the use of GnRH agonist or antagonist. During the IVF
process, once it is determined the eggs are mature (by ultrasound
assessment of the follicles and measurement of estradiol), this
signal is given by the injection of human chorionic gonadotropin (hCG).
The timing of this injection is very important. Spontaneous
release of the eggs will begin at about 38-40 hours after this
injection. It is necessary to retrieve the egg BEFORE ovulation has
taken place. It is realized that the closer to ovulation the
retrieval is performed, the greater the success of fertilization.
Timing is critical. Therefore, in rare instances ovulation may occur
naturally before retrieval is possible.
During a transvaginal retrieval, a needle is inserted through the
vagina under sonographic (ultrasound) guidance, and into the
follicle (fluid collection) so the egg and follicular fluid may be
aspirated. The egg itself can be seen only under the microscope once
the fluid is taken into the laboratory (see Figure 3). Spinal
anesthesia or IV sedation will be used for these procedures.
A laparoscopic retrieval will only be used under special
circumstances. During laparoscopy, an instrument which permits the
telescopic viewing of the follicles is inserted through the abdomen.
A needle is introduced through a second incision and placed into the
follicle. The egg and the follicular fluid can then be aspirated.
Transvaginal Oocyte Retrieval Procedure
Figure 3 Reprinted with permission from Organon
The oocytes are retrieved in one of two ways: through a surgical
procedure called laparoscopy or through transvaginal retrieval by
ultrasound guidance. Ultrasound-guided retrieval has become the
standard for almost all procedures.
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