The Menstrual Cycle and IVF Initiation
Cycle Day 1
This is defined as the first day of a woman’s menstrual period. It is the starting point for calculating IVF days. On this day, the body begins a new hormonal cycle, with follicle-stimulating hormone (FSH) levels starting to rise. For example, a woman who starts her period on the 1st of a month will mark that as Cycle Day 1 for her IVF cycle.
Ovarian Stimulation
Usually, a few days after Cycle Day 1, ovarian stimulation begins. This is a crucial step where medications like gonadotropins are administered to encourage the ovaries to produce multiple eggs. The dosage and duration of stimulation depend on various factors such as the woman’s age, ovarian reserve, and previous IVF attempts. For instance, a younger woman with a good ovarian reserve may require a shorter stimulation period compared to an older woman with diminished ovarian function.
Monitoring the Ovarian Response
Ultrasound Scans
These are performed regularly, usually starting around Cycle Day 5 or 6. The purpose is to measure the size and number of developing follicles in the ovaries. The doctor can assess if the follicles are growing at an appropriate rate. For example, if the follicles are not growing as expected, the dosage of the stimulation medications may need to be adjusted.
Hormone Level Checks
Blood tests are done to measure hormone levels such as estrogen and luteinizing hormone (LH). Estrogen levels increase as the follicles grow, and a sudden rise in LH may indicate that ovulation is about to occur prematurely. If LH levels spike too early, medications like GnRH antagonists may be given to prevent premature ovulation.
The Trigger Shot and Egg Retrieval
Timing of the Trigger Shot
This is calculated based on the follicle size and hormone levels. It is usually given when the follicles have reached an appropriate size, typically around 18-20 millimeters in diameter. The trigger shot contains human chorionic gonadotropin (hCG) or a similar hormone, which mimics the natural LH surge and triggers the final maturation of the eggs. For example, if the follicles are of the right size and the estrogen levels are satisfactory on Cycle Day 12, the trigger shot may be administered on that day.
Egg Retrieval
Approximately 36 hours after the trigger shot, egg retrieval is performed. This is a minor surgical procedure where a thin needle is inserted through the vaginal wall into the ovaries to aspirate the mature eggs. The eggs are then immediately taken to the laboratory for further processing.
Fertilization and Embryo Development
Fertilization
In the laboratory, the eggs are combined with sperm. This can be done through conventional insemination, where sperm are placed in a dish with the eggs, or through intracytoplasmic sperm injection (ICSI), where a single sperm is directly injected into an egg. The day of fertilization is usually considered Day 1 of embryo development.
Embryo Culture
The embryos are then cultured in a special incubator. Over the next few days, they divide and develop. On Day 3, the embryos are typically at the 6-8 cell stage, and on Day 5, they may reach the blastocyst stage. The embryologist closely monitors the embryos’ development and grades them based on their quality and appearance.
Embryo Transfer
Fresh Embryo Transfer
This can be done on Day 3 or Day 5 after egg retrieval. The choice depends on various factors such as the number and quality of the embryos. If the embryos are developing well and the woman’s uterine lining is suitable, a Day 5 blastocyst transfer may be preferred as it is believed to have a higher implantation rate. For example, if the embryos have reached the blastocyst stage and the endometrium is thick enough on Day 5, the transfer can proceed.
Frozen Embryo Transfer
If the embryos are frozen for later use, the transfer is scheduled according to the woman’s menstrual cycle and the clinic’s protocol. The woman may need to take medications to prepare the uterine lining before the transfer. The thawing and transfer process is carefully timed to ensure the best chance of implantation.
The Post-Transfer Period and Pregnancy Testing
Luteal Phase Support
The woman is usually given medications like progesterone to support the luteal phase of the menstrual cycle and help with implantation. This support continues for several weeks. For example, progesterone may be administered in the form of injections, vaginal suppositories, or tablets.
Pregnancy Testing
A blood test for human chorionic gonadotropin (hCG) is usually done around 10-14 days after embryo transfer to determine if pregnancy has occurred. If the hCG levels are above a certain threshold, it indicates a positive pregnancy. Follow-up ultrasounds are then done to confirm the presence and viability of the pregnancy.
Conclusion
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