In Vitro Fertilization requires the removal of mature eggs from the ovaries with an immediate transfer of these eggs to the embryology laboratory for culture. The egg retrieval is usually planned to occur about 35-36 hours following the onset of the LH surge (or hCG injection). By this time, the egg is (ideally) floating freely within the follicular fluid after having been released from its attachment to the wall of the growing follicle. Simple aspiration of the follicular fluid typically retrieves the (accompanying) egg.
Most IVF centers use an ultrasound guided transvaginal approach for oocyte (egg) retrieval. Advantages of transvaginal ultrasound guided egg retrieval include: (a) aspiration of follicles can be accomplished under direct (ultrasound) guidance (the doctor actually watches the needle enter the follicle to aspirate the fluid on a monitor), (b) a high percentage of eggs typically are successfully retrieved from mature follicles, (c) the procedure is well tolerated by patients with only IV sedation or local anesthesia, and (d) it has very few complications.
Prior to the availability of transvaginal ultrasound guided egg aspiration, laparoscopy was required for these (egg) retrievals. The disadvantages of laparoscopy include that it: (a) requires general anesthesia, (b) is a true (same day) surgical procedure, (c) requires that the ovary be punctured in areas that “appear fruitful” when examining the outside of the ovary directly (but it is impossible to appreciate the follicule’s depth and smaller follicles under the outer ovarian cortex are difficult to aspirate), and (d) it has greater rates of complication compared to ultrasound guided egg aspiration.
Concerns during the aspiration of ovarian follicles include: (a) use of a sharp needle (critical since a sharp needle will more easily penetrate the ovaries which are generally mobile organs), (b) avoiding endometriomas (ovarian “chocolate cysts” related to endometriosis) since their contents may be embryotoxic and may contaminate the follicular fluid of subsequent follicles that are aspirated, (c) limiting aspiration of blood (occassionally unavoidable) since it may have some embryo toxicity if entered into the culture medium (lower fertilization of accompanying eggs has been reported), and (d) flushing of the follicles with culture medium, which will sometimes result in aspiration of eggs otherwise “lost” or irretrievable (reports suggest that routine flushing is not clinically beneficial).
Complications can occur during egg retrieval but generally these are uncommon. These complications include the risks of all surgical procedures, which includes infection, bleeding and inadvertant injury to surrounding tissues.
Serious infections have been reported following egg retrieval procedures when prophylactic antibiotics were not used. The rate of tubo-ovarian abscess formation in two large series of ultrasound guided transvaginal egg retrievals is between 0.2 and 0.3% and may become clinically apparent up to 6 weeks following the procedure. There are reports of at least two total abdominal hysterectomies performed for such infections. When antibiotics are given 30-60 minutes prior to the procedure, the incidence of infection is limited and is very uncommon.
The ultrasound guided aspiration of eggs is performed while (directly) watching the needle enter the ovarian follicles. However, injury to surrounding blood vessels remains possible. On occasion the blood vessel will look similar to a follicle (if the transducer of the ultrasound probe “cuts” a crosssection of the vessel rather than a longitudinal section) and this may then be entered “unintentionally.” The incidence of serious hemoperitoneum (free blood in the pelvis or abdomen) in the two large reports of transvaginal ultrasound guided egg aspirations is 0.6% (about 1 in 200) with half of these treated with laparoscopy and the remainder requiring a laparotomy.
(3) Inadvertant Injury to Surrounding Tissues
It is possible to puncture the bowel during the egg retrieval, especially if the woman has known dense bowel adhesions around her ovaries. Unrecognized bowel puncture may be far more common than we know, with small needle stick injuries usually not requiring repair. Bowel injury requiring repair is very uncommon.
It is also possible to lacerate or puncture the ureter during egg retrieval. Occasionally the ovary will be fixed in place along the uterus or in the pelvis such that the needle is passed through the uterus or cervix. Ureteral injury is possible during these very difficult cases but is very uncommon.