The oocyte retrieval (pick-up) in an assisted fertilization process: what does it consist of?

In vitro fertilization treatment involves the woman undergoing controlled ovarian stimulation in order to produce as many follicles as possible.

The more follicles that mature, the more oocytes can be retrieved at the time of collection. In this way, the chances of obtaining fertilized oocytes and arriving at blastocysts increase.

Controlled ovarian stimulation requires the woman to follow a specific therapeutic plan: the injection of drugs under the skin at precise intervals of time. According to the doctor’s indications, the woman will have to undergo frequent ultrasound scans and blood samples to check the level of three hormones in particular: progesterone, LH and estradiol.

During the assisted reproduction process , most women will take ovarian stimulation drugs for about 8-14 days, with the aim of maturing as many oocytes as possible without incurring the risk of hyperstimulation . The more mature oocytes are recovered, the more chances of pregnancy there are.

In a woman who responds well to stimulation (the so-called normal responder ), an average of 10-20 oocytes are recovered. However, not all of them are usable since usually only 75% of large follicles produce a “mature” oocyte (the presence of a polar body is noted when analyzed under a microscope).

Once the ultrasound determines that there are a satisfactory number of follicles with the right size (at least 17 mm in diameter), the doctor will indicate to the woman the exact moment to induce ovulation through an injection of HCG.

This hormone replaces the natural increase in luteinizing hormone (LH), an increase which is pharmacologically blocked during stimulation, and stimulates the final stage of oocyte maturation, because only in this way can they then be fertilized in vitro.

Generally, the oocyte retrieval surgery is scheduled about 34 hours after the injection of HCG.

The intervention of the oocyte retrieval

It is an operation performed in the operating room under sedation, to collect the contents of the mature ovarian follicles, and consequently the oocytes. The intervention, in the absence of complications (which are very rare), provides for the woman’s resignation during the same day of hospitalization.

The timing of the oocyte retrieval from the follicles is very important, and is closely related to the injection of HCG. In fact, it is performed about 34 hours after the puncture, before the follicles burst.

The operation is performed by a specialized gynecologist under ultrasound guidance, all transvaginally.

Ultrasound allows you to visually guide a small needle through the upper part of the vagina, first into one ovary and then into the other. Through the needle connected to an aspiration system, the liquid is taken from the follicles, one after the other. The liquid is directly aspirated into the test tubes.

The whole process usually takes less than 30 minutes.

You may feel small cramps the day of the procedure and the day after, and you may have vaginal discharge. The woman may also experience a feeling of fullness and/or pressure due to the ovaries being expanded by ovarian stimulation. This feeling can last for a few weeks.

The test tubes must be delivered directly to the biological laboratory. Here the follicular fluid will be immediately analyzed by an embryologist and the oophorus heaps containing the oocytes will be recovered. The number of oocytes retrieved and their stages of maturation are carefully recorded.

The number of oocytes produced and retrieved is influenced by the patient’s age, ovarian reserve, type of stimulation and response to ovarian stimulation, and occasionally by the accessibility of the ovaries to the needle . For example, in severely obese women, egg retrieval can be complicated.