In vitro fertilization (IVF) is a form of assisted reproductive technology where an egg is fertilized with sperm in a controlled laboratory environment before transferring the resulting embryo into the uterus. This process is designed to help individuals and couples experiencing difficulties conceiving.

The IVF process begins with ovarian stimulation, during which reproductive endocrinologists prescribe hormonal medications to stimulate the ovaries to produce multiple eggs instead of the single egg released during a natural cycle. This increases the likelihood of successful fertilization and embryo development.

Once the ovaries have been sufficiently stimulated, the next step is oocyte retrieval. This procedure typically occurs approximately 36 hours after the triggering injection to induce final egg maturation. A transvaginal ultrasound is performed to visualize the ovaries. Using a needle guide, a physician carefully inserts a thin needle through the vaginal wall and into the ovarian follicles, where the mature eggs reside. The needle aspirates the follicles, collecting the oocytes and the follicular fluid. This process is done under sedation or anesthesia to minimize discomfort for the patient.

After retrieval, the oocytes are placed in a specialized culture dish, where they will be fertilized. In conventional IVF, the retrieved oocytes are incubated with a prepared sperm sample (containing approximately 50,000 to 100,000 sperm cells for 12 to 18 hours, allowing natural fertilization.

In cases where male infertility is a factor, a more specialized technique called intracytoplasmic sperm injection (ICSI) may be utilized. This method involves selecting a single, healthy sperm and directly injecting it into the cytoplasm of a mature egg using a fine glass needle. ICSI improves the likelihood of fertilization, particularly in situations involving low sperm count or poor sperm quality.

After fertilization, the resulting embryos are monitored for development over several days. Embryologists assess their growth and quality, determining the optimal time for transfer. The embryos can be transferred at different developmental stages, such as the cleavage stage (typically 3 days post-fertilization) or the blastocyst stage (about 5 days post-fertilization). Blastocyst transfers are often preferred due to higher implantation rates.

The final step in the IVF process is the embryo transfer. This procedure is performed in a sterile environment, usually done in conjunction with a transabdominal ultrasound for guidance. A thin catheter is inserted through the cervix into the uterus, and the selected embryos are gently placed into the uterine cavity, ideally within 1 to 2 centimeters of the uterine fundus, the upper part of the uterus. Following the embryo transfer, a pregnancy test is typically conducted around two weeks later to determine if implantation has occurred and if the woman is pregnant.