Before starting fertility treatment, it's important to have a good understanding of the menstrual cycle. Knowing the similarities and differences between a natural cycle and a fertility treatment cycle can help you feel more comfortable with the process. In this post, we'll dive into the fascinating world of hormonal changes that regulate the menstrual cycle and explore how these hormones are utilized in fertility treatments like frozen embryo transfer (FET).
The Follicular Phase
The menstrual cycle begins with the follicular phase, during which the ovary contains small fluid-filled structures called follicles. Each follicle produces estrogen and houses an immature egg. Follicle stimulating hormone (FSH), released by the pituitary gland, stimulates the growth of a single follicle in one ovary over about 14 days. As the follicle matures, it produces more estrogen, causing the uterine lining (endometrium) to thicken in preparation for a potential fertilized egg.
Ovulation
When the follicle is fully mature and estrogen levels are high, luteinizing hormone (LH) production rises sharply, triggering ovulation. During ovulation, the mature egg is released from the ovary into the fallopian tube, where it can be fertilized by sperm. Fertilization must occur within about 24 hours of ovulation, or the egg will degenerate, and pregnancy will not occur.
The Luteal Phase
After ovulation, the menstrual cycle enters the luteal phase. The remnants of the follicle develop into a structure called the corpus luteum, which produces both estrogen and large amounts of progesterone. Progesterone plays a crucial role in maturing and maintaining the endometrium. If fertilization does not occur, the corpus luteum degenerates after about 14 days, causing progesterone levels to drop, and the uterine lining to shed, marking the start of a new menstrual cycle.
Implantation and HCG
If fertilization occurs, the resulting embryo enters the uterus from the fallopian tube after about six days and may implant in the uterine lining. Upon implantation, cells in the outer layer of the embryo begin producing human chorionic gonadotropin (HCG). HCG continuously stimulates the corpus luteum to produce more progesterone, preventing the loss of the uterine lining and supporting the early stages of pregnancy.
The Role of Hormones in Fertility Treatment
The hormones produced in a typical menstrual cycle are also used in fertility treatments. FSH injections are used to increase egg numbers. Estrogen and progesterone are often used in FET to better time the procedure and improve the uterine lining. By understanding the role of each hormone, you can better comprehend how fertility treatments work and why certain medications are used at specific times during the process.
Conclusion
The menstrual cycle is a complex and fascinating process regulated by a delicate balance of hormones. By understanding the roles of FSH, LH, estrogen, progesterone, and HCG in a natural cycle, you can better grasp how fertility treatments like FET work to support the growth of a healthy uterine lining and improve the chances of a successful pregnancy.
The content on this blog is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always consult with a qualified healthcare provider before making any health-related decisions or implementing any medical information shared here.