Menstrual Cycle- Written by a specialist.

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Menstrual Cycle- Written by a specialist.

Menstrual Cycle

By Fertility Cloud Head Nurse Svetlana Izrailevsky, BSN, RN.

What is a menstrual cycle?  In reality, a menstrual cycle consists of 3 broad categories of cycles:  hormones, ovarian (follicular) cycle, Endometrial lining cycle, and Cervical mucus development cycle.  It is important to understand that these cycles are taking place in tandem, in parallel and in relationship to each other.  That means that what happens in one of these cycles will affect the developments in the other ones.  

First, lets review the hormones involved in the menstrual cycle:

FSH–FSH helps control the menstrual cycle and stimulates the growth of eggs in the ovaries. FSH levels in women change throughout the menstrual cycle, with the highest levels happening just before an egg is released by the ovary. This is known as ovulation.

LH– LH helps control the menstrual cycle. It also triggers the release of an egg from the ovary. This is known as ovulation. LH levels quickly rise just before ovulation.

Estradiol, also called E2, is the main estrogen in nonpregnant females of childbearing age. It’s mostly made in the ovaries and is important for uterine lining development.

Progesterone is a hormone that’s made mainly by the ovaries. Each month, progesterone prepares your uterus for pregnancy. During a normal menstrual cycle, an ovary releases an egg and your progesterone levels begin to rise. Progesterone makes the lining of your uterus grow thicker so that a fertilized egg can attach (implant) inside of the uterus and grow into a baby. If you don’t become pregnant, your progesterone levels will fall. The lining of your uterus will become thinner again. When your uterus starts to get rid of the extra blood and tissue, your menstrual period will begin.  If you become pregnant, progesterone levels will continue to rise to about 10 times higher than usual to support the pregnancy.

Now, lets us look at the 3 main time frames of the cycle:

These different cycles communicate via hormone messengers. For example, when the egg inside the follicle is mature, it sends a signal to the pituitary gland via the increased levels of Estradiol hormone. This stimulates the rise in LH hormone levels which finishes the maturation of the egg and allows it to break out of the follicle–ovulate. At the same time, Progesterone level rises to support the uterine lining and the uterine lining undergoes a transformation where the recetors for the embryo become activated and stand ready.

The diagram below illustrates how the different cycles are connected:



LET’S LOOK AT SOME COMMON QUESTIONS THAT COME UP:

  • What is the best time to get pregnant during my cycle? What should I be doing to maximize the potential for conceiving?

When we are speaking of a regular 28-30 day cycle, your fertility window is between cycle day 10-15.  We would recommend intercourse every other day starting on cycle day 10.  Once you note your LH surge by using ovulation predictor kits, you should have intercourse daily on the day of the LH peak/surge and the subsequent 2 days.  

Please remember that LH hormone stays elevated for a very short time, just about 24 hours so we do not recommend that you keep checking your LH after you see the peak.  

Male partners, if applicable, should do ejeculation every 2-3 days starting with your cycle day 1.  We would like to have the freshest sperm sample available for insemination.  Please do not hold off on regular ejeculation because that increases the number of dead and dying sperm in the sperm sample that will be produced for the insemination.

  • Wait!  What if my cycles are not regular?

For some patients, the cycles are regular and predictable, but long.  It is possible to have a regular ovulatory cycle with the overall length of 35 days, for example.  However, there are also women who have irregular ovulatory cycles due to ovarian dysfunction.  This dysfunction is usually related to improper hormone levels of Estradiol and FSH.

  • What does the follicle stimulating hormone (FSH) do again?

FSH–FSH helps control the menstrual cycle and stimulates the growth of eggs in the ovaries. FSH levels in women change throughout the menstrual cycle, with the highest levels happening just before an egg is released by the ovary. This is known as ovulation.  

  • What about Estradiol?

Estradiol, also called E2, is the main estrogen in nonpregnant females of childbearing age. It’s mostly made in the ovaries and is important for uterine lining development.  As you can see in the diagram above, Estradiol rises slowly before ovulation and stays elevated for a period of about 7 days after the ovulation.  This is so that there is no ovarian follicular recruitment happening during the period of potential fertilization and implantation.   Elevated levels of Estradiol can interfere with production of FSH so if the Estradiol levels are high at the beginning of the cycle, the regular growth and development of the follicles can be impacted. 

Estradiol can be elevated as a result of conditions such as polycystic ovarian syndrome (PCOS) or presence of elevated levels of BPA in the system. Bisphenol A (BPA) is a chemical produced in large quantities for use primarily in the production of polycarbonate plastics. It is found in various products including shatterproof windows, eyewear, water bottles, and epoxy resins that coat some metal food cans, bottle tops, and water supply pipes. https://www.niehs.nih.gov/health/topics/agents/sya-bpa/index.cfm.  

  • I ovulated 2 days past normal ovulation days, does that mean my period will start two days later than expected?

The next menstrual period will start once the Progesterone and Estradiol levels fall, if there is no conception.  They typically occur 10-14 days after ovulation occurs.  If you ovulate 2 days later than you usually do, your menses might be delayed accordingly.

  • I have been taking Progesterone to support my uterine lining.  Will that impact my menses?

Yes!  If you are taking Progesterone, you are not likely to start menses even if you are not pregnant. You will be asked to do a home pregnancy test and stop  taking the Progesterone if the test is negative.  You can expect your menses 2-5 days after stopping the medication.  Some patients may begin spotting even before stopping Progesterone.  The spotting/bleeding you will get after the Progesterone may be a little heavier than your usual menses and the first day of bleeding will count as cycle day 1 for next treatment.

  • It was my first time taking Clomid, is it normal that I expect menses to be delayed even with negative HPT?

Clomid does not directly impact the length of menses.  However, it does help regulate the ovulatory process so your menstrual cycle will look different.  For some patients, cycles are a bit shorter and for others they are longer as Clomid works to increase production of FSH hormone.

  • What does LH hormone timing look like in the cycle?

LH rises slowly only a few days before ovulation and then has a sharp rise known as LH peak or surge, 24-36 hours before ovulation.  It only stays elevated for about 24 hours and then drops sharply.  It does not begin to rise again with the start of the menses, at least not right away.