In IVF treatment, in almost all cases, it is essential to stimulate the ovary to support multiple follicular growth and have more than one oocyte to use. This strategy derives from the evidence that not all oocytes are of good quality, and in vitro fertilization of the oocyte does not always produce a good-quality embryo transferable into the uterus. In a natural ovarian cycle, average concentrations of follicle-stimulating hormone ( FSH ) allow the growth of a single ovarian follicle, the one most sensitive to the action of the same hormone.
For this reason, developing multiple follicles requires the exogenous administration of FSH. In stimulation cycles, the hormone is administered in ways that make it available in circulation at supra-physiological concentrations and for a sufficient number of days so that not only do multiple follicles grow but also reach a follicular size that allows the final maturation of the oocyte. Luteinizing hormone ( LH ) is sometimes also administered to support follicular function. A critical aspect of ovarian stimulation is preventing increasing estrogen concentrations produced by growing follicles from causing premature and spontaneous ovulation.
IVF: Egg Collection
Oocyte collection takes place 36-38 hours after the administration of hCG. At this time, the oocytes have already benefited from the final maturation action promoted by the follicle, the action of which was previously stimulated by hCG. Still, they have not yet been released from the follicle itself. The collection is moderately invasive. It requires transvaginal ultrasound guidance and is performed using a needle connected to a suction system. Passed into the vagina, the needle reaches the follicles to be aspirated after passing through the vaginal wall. The “Genova Fertility Centre” aspiration procedure is usually quick (15-20 minutes in total), and the risks of bleeding or infection associated with this procedure, performed by expert doctors, are scarce (less than 1 in 20,000). However, oocyte collection requires analgesics or deep sedation to avoid unnecessary stress for the patient. The contents of the follicles are conveyed through a system of tubes connected to the aspiration needle and collected in a series of test tubes maintained at a temperature suitable for the oocytes (37°C). Once collected, the follicular contents are transferred to the ART laboratory, where the oocytes are identified and cultured in preparation for in vitro fertilization.
In vitro fertilization: preparation of sperm
In addition to the growth, maturation, and collection of oocytes, IVF requires the preparation of spermatozoa. Spermatozoa present in freshly ejaculated semen do not possess the capacity to fertilize, a function that is acquired in vivo only after a few hours of permanence in the female genital tract. The discovery of this phenomenon, known as capacitation, represented a fundamental advance for ART.
In the ART laboratory, capacitation is obtained by separating the spermatozoa from the rest of the semen sample and subsequently exposing them to specific culture conditions. The technique known as “swim-up” requires that the semen is placed on the bottom of a test tube and that an equivalent volume of culture medium is layered on top of it, taking care to keep the interface between the two fluids well-defined. This allows the motile spermatozoa, which are typically also the most vital, to migrate from the semen to the culture medium, determining their separation from the liquid part of the semen analysis test price from the immotile spermatozoa and various other cellular or corpuscular impurities.
In vitro fertilization: transfer of the embryo into the uterus
Embryos obtained after in vitro fertilization can be transferred into the uterus at any time during in vitro development, starting from the second day. Still, the transfer is usually done on the third or fifth day. To avoid the occurrence of triplet or higher-order pregnancies, current good medical practice rules recommend transferring a maximum of two embryos, with some exceptions.
The act of transfer is manual and straightforward.
The embryo is taken from the culture dish and loaded by the embryologist into a catheter that is then delivered to the doctor. Finally, sometimes, under ultrasound guidance, the doctor deposits the embryo in the patient’s uterus by passing the catheter. The whole thing is completed quickly and painlessly. To support uterine function in the event of implantation, the patient is asked to follow progesterone therapy for at least 15 days after the transfer. At this time, the first pregnancy test is performed. From this moment on, in the event of pregnancy, the process is identical to any pregnancy obtained naturally.
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