It is important to understand the menstrual cycle in order to know what is normal and be able to identify when you may have an issue. The menstrual cycle relies on a symphony of hormones, which use specific timing and hormone levels in order to grow a follicle, mature an egg and prepare your uterus for implantation.
What you see from the outside should be a regular monthly bleed of bright red blood and moderate volume, lasting 2-3 days with some light bleeding on one day either side. The healthy menstrual period should occur around 28-30 days from the start of the previous bleed. The menstrual period is the shedding of the dead lining from the uterus. Hormone rise and fall orchestrates the growth and expulsion of the lining, if no conception takes place.
The purpose of the uterus is house a fetus for 9 months as it grows into a baby. The growing fetus needs to receive resources and fuel to grow, which is provided by the placenta. The role of the uterine lining is to provide a nutrient exchange surface between the placenta and the mother. This allows a good blood supply to her menstrual lining, which in turn feeds the placenta and sends those nutrients to the fetus via the umbilical cord.
Every month a new egg grows and the uterus prepares a new lining in conjunction with the growing egg. If that egg is not fertilized there is no need for a lining, so it dies with the egg and is expelled as the menstrual period. There are 3 phases to each cycle, the first is lining growth, second is lining maturation and the third is the shedding. Phase one is stimulated by the hormone estrogen and phase two by the hormone progesterone. The third phase (shedding of the lining or menstrual period) results from a sudden drop off in the levels of progesterone and estrogen and the end of a cycle.
Ovary, Egg and Follicle
As mentioned previously the lining growth phases coincide with the egg growth. The egg also goes through 3 phases - the follicle growth phase on the ovary, the post-ovulation phase in the tube, death and shedding with the menstrual period.
In the ovary, eggs are made when a woman was a fetus in her mother’s uterus. Each menstrual cycle is governed by the waking up of an egg thats grows inside a protective and hormone-producing house called the follicle. Stimulation triggers from the brain wake up the follicle at the start of a cycle, which produces the estrogen necessary to grow both the egg and lining. This phase should take approximately 14 days and the follicle can grow as big as 1 inch before it bursts in an event called ovulation. Ovulation is designed to release the egg from the follicle where it is released into the fallopian tube. The fallopian tube is a passage that joins the ovary to the uterus and it is also where the sperm meet the egg during fertilization.
Phase two is the journey of the egg through the tube, where it can either meet sperm and undergo fertilization or travel for 6-7 days down the tube and into the uterus unfertilized. During this 6-7 days, the remains of the follicle still on the ovary makes progesterone, which matures the uterus lining. This occurs so that the lining can change from the growing phase, while the egg is also growing, to the maturing phase after ovulation, while the egg is traveling through the tube. If the egg is fertilized, the mature lining should be ready to implant this fertilized egg, now called an embryo, when it reaches the uterus. If the egg is not fertilized, the ovary stops producing progesterone and estrogen when implantation does not occur, and the cycle comes to an end as the levels of the hormones become very low. The egg dies, the remains of the follicle dies and the lining dies. The lining then takes 3-5 days to bleed out of the uterus, which is the menstrual period.
The Two Parts Of The Menstrual Cycle
The first part of the ovulation cycle is called the follicular phase. This phase starts the first day of the last menstrual period (LMP) and continues until ovulation. This first half of the cycle can differ greatly for each woman lasting anywhere from 7 days until 40 days. The second half of the cycle is called the luteal phase and is from the day of ovulation until the next period begins. The luteal phase has a more precise timeline and usually is only 12-16 days from the day of ovulation. This ultimately means that the day of ovulation will determine how long your cycle is. This also means that outside factors like stress, illness, and disruption of normal routine can throw off your ovulation which then results in changing the time your period will come. So the old thought that stress can affect your period is only partly true. Stress can affect your ovulation which ultimately determines when your period will come, but stress around the time of an expected period will not make it late -- it was already determined when it would come 12-16 days earlier!
Fertility Awareness is one way to track when ovulation occurs, and it includes studying the changes in cervical mucus and using a basal thermometer. Cervical fluid will change to a wet, slippery substance that resembles "egg whites" just before ovulation occurs and until ovulation is over. A basal thermometer helps track a body temperature rise, which signals that ovulation has just occurred.
Another way to track ovulation is through ovulation kits and fertility monitors. These can be Purchased Online. Tracking ovulation can help a woman get a better idea of when pregnancy can and cannot occur during her monthly cycle. Once ovulation has occurred, there is nothing you can do to increase your chances of pregnancy. Your next step is to begin watching for early pregnancy symptoms.
From the Menstrual Period to Ovulation (the details you may not know!)
When your menstrual cycle begins, your estrogen levels are low. Your hypothalamus (which is in charge of maintaining your hormone levels) sends out a message to your pituitary gland which then sends out the follicle stimulating hormone (FSH). This FSH triggers a few of your follicles to develop into mature eggs. One of these will develop into the dominant follicle, which will release a mature egg and the others will disintegrate. As the follicles mature they send out another hormone, estrogen. The high levels of estrogen will tell the hypothalamus and pituitary gland that there is a mature egg.
A luteinizing hormone (LH) is then released, referred to as your LH surge. The LH surge causes the egg to burst through the ovary wall within 24-36 hours and begin its journey down the fallopian tube for fertilization. The follicle from which the egg was released is called the corpus luteum, and it will release progesterone that helps thicken and prepare the uterine lining for implantation. The corpus luteum will produce progesterone for about 12-16 days (the luteal phase of your cycle.) If an egg is fertilized, the corpus luteum will continue to produce progesterone for a developing pregnancy until the placenta takes over. You can begin looking for pregnancy symptoms as early as a week after fertilization. If fertilization does not occur the egg dissolves after 24 hours.
At this time your hormone levels will decrease and your uterine lining will begin to shed about 12-16 days from ovulation. This is menstruation (menstrual period) and brings us back to day 1 of your cycle. The journey then begins all over again.
The time of ovulation is one of the most important things a woman should understand about her body, since it is the determining factor in getting pregnant and preventing pregnancy. The process can be confusing and somewhat overwhelming when trying to understand. The Association recommends using an ovulation kit or fertility monitor to maximize your chances and to confirm when your ovulation is occuring. There are many frequently asked questions about the ovulation process, and the Association has attempted to address those for you. If you still have further questions regarding ovulation, we encourage you to either talk with your healthcare provider or contact the American Pregnancy Association for more information. Being informed on what your body does can help you feel more in charge of your health.