Oocyte retrieval — the process of collecting mature eggs directly from a woman's ovaries — is performed as a prerequisite for in vitro fertilization (IVF), surrogacy or cryopreservation.
This procedure originally used laparotomy and other related techniques. In 1984, ultrasound was found to improve the visualization and accuracy of needle placement into the ovarian follicles to retrieve a greater number of oocytes in each procedure.
Transvaginal vs. Transabdominal Ultrasound
Oocyte retrieval can be done by either transvaginal ultrasound (TVUS) or transabdominal ultrasound (TAUS) depending on a number of factors, such as ovary location, patient body habitus, and the presence of pre-existing conditions such as endometriosis, ovary transposition, hysterectomy or mullerian agenesis.
TAUS sends a beam of ultrasound waves through the anterior abdominal wall, over the area of the urinary bladder and female reproductive organs. When the bladder is distended, it acts as an acoustic window that allows ultrasound energy to pass through it with minimal attenuation.
The transabdominal approach can evaluate the overall pelvis, the distended bladder, and the uterus and ovaries. This method is especially useful in accessing ovaries that have been transposed up higher in the pelvis, either during surgery or a previous pregnancy.
A full bladder is not required for the transvaginal ultrasound procedure. Within the vaginal canal, the distance to the pelvic organs is reduced and higher ultrasound frequencies can therefore be used, providing better resolution.
The transvaginal ultrasound is limited to assessing a smaller area within the lower pelvis, where the uterus and ovaries are typically located. The image is often more detailed, but not able to visualize the upper pelvis.
The Oocyte Retrieval Process
The transvaginal ultrasound approach is more commonly done for oocyte retrieval. In certain situations where the ovaries are not vaginally accessible, a transabdominal approach is used.
Ovaries can be difficult to see when there is a history of pelvic surgery that has caused ovary displacement, or when there is increased body habitus resulting in anatomic distortion. The TAUS approach can help add to the number of oocytes retrieved over the standard TVUS method when ovaries are difficult to visualize.
According to the Taiwanese Journal of Obstetrics and Gynecology, the average procedure time of the TVUS procedure is 20.2 minutes whereas TAUS is 28.2 minutes. Post-surgical symptoms of pain and bleeding are both typically mild and comparable. Recovery time between the two is also similar.
The Patient Perspective
Despite the usefulness of TVUS from a medical perspective, some women may find it painful, intrusive or embarrassing. Considering the perspective of the patient and their comfort level in the situation is important.
Most women who have experienced a TVUS found it to be somewhat uncomfortable or mildly painful, as reported by Obstetrics and Gynecology. Almost all women were willing to undergo a transvaginal ultrasound in the future, however, if their physician recommended the procedure.
This study also found that patients were most comfortable when a transvaginal ultrasound was accompanied by clear information about the exam, was treated with sensitivity and dignity in a private and relaxed environment, and when the exam time was kept to a minimum.
The Physician Perspective
While both patient concerns and the optimal outcome should be considered, the physician will ultimately make the best surgical decision based on ovary location, body habitus, any patient-specific risk factors and their own past experience of the procedure.
The addition of TAUS to the typically done TVUS can ensure that enough oocytes are retrieved to make possible a successful IVF, surrogacy or cryopreservation. Either way, ultrasound provides the safest and most efficient method of oocyte retrieval because it allows for the best visualization of the needle tip during surgery.
With these two techniques having similar post-surgical symptoms and recovery time, the main consideration is maximizing the number of oocytes harvested while minimizing damage to surrounding tissues and post-surgical complications — something that ultrasound has been helping to make possible in all healthcare fields.
