Understanding Ovulation And Your Menstrual Cycle

Your cycle consists of several key phases, the first being the follicular phase, which starts with your period and ends with ovulation. Named for egg development, this phase begins with cycle day one — your first day of full-flow — and should last approximately 2 weeks (10-17 days).

It can also be shorter or much longer in someone with an irregular cycle. In an ideal cycle, your period should begin a brilliant bright red and last for approximately 4-5 days with little to no clotting, spotting, cramping or pain.

At the beginning of each new cycle, every woman starts with a base number of antral follicles (AFC) observable via ultrasound on each ovary. 

These follicles release anti-mullerian hormone (AMH). Both AFC and AMH can fluctuate in either direction from cycle to cycle, but do tend to decrease overall as we age; these changes don’t necessarily follow a linear path. In a natural, unmedicated cycle, a woman will typically have one dominant follicle emerge and grow leading up to ovulation. 

That said, it takes approximately 90 days for an immature follicle to produce a fully mature egg that is ready to ovulate (Williams and Erickson). This is important, because what a woman does during that 3 month window can positively impact her follicles, regardless of her age.

On occasion, a woman may have more than one mature follicle and hyperovulate, with a higher chance of conceiving multiples. Although rare in natural cycles, hyperovulation is more likely to happen in older women, due to heredity or as a result of taking fertility drugs.

Meanwhile, the brain’s hypothalamus releases hormones and growth factors via the pituitary to aid in egg development at the site of each ovary. Follicle stimulating hormone (FSH), for example, stimulates both the follicles to mature and the ovaries to release estrogen.

Estrogen rises in accordance with the size and number of follicles developing and also plays a role in building and thickening the endometrial lining. We’ll circle back as to why this is important when we get to the luteal, or progesterone-dominant, phase of the cycle.

Once ovulation is complete, an organ called the corpus luteum forms from the collapsed follicle that released the egg. This marks the beginning of the Luteal Phase, the progesterone-dominant phase of a woman’s cycle. Ideally, the corpus luteum should release progesterone for a minimum of 12-14, or up to 17 days.

If the embryo implants successfully, it should continue to stimulate the corpus luteum via human-chorionic-gonadotropin (HCG) to keep producing progesterone. If HCG isn’t present, hormone levels will drop and the lining will begin to shed signaling the start of a new cycle via menstruation.

When implantation successfully takes place, progesterone stays high and HCG will begin to rise. Some women see positive pregnancy tests days before a missed period, if implantation happens early enough. Additionally, a healthy, sufficient, trilaminar lining is imperative for this process to work. Adequate blood flow is also important, which is why fibroids and polyps can sometimes block embryo development.

While progesterone plays a key role in keeping the lining in-tact, it also helps the lining become receptive and ready to receive a healthy embryo. Most of the time, implantation happens approximately 8-10 days post ovulation. Although uncommon, some women may notice pain or spotting during this time. 

These symptoms may be brief, but they can also continue on into the first trimester of pregnancy and are not considered to be abnormal. Subchorionic hematoma is another common, relatively harmless reason some women experience bleeding in the first trimester.

Every now and then, for some, it can be difficult to determine if these early symptoms are due to pregnancy or to an oncoming period. Most of the time, if a sperm and egg create an embryo that is chromosomally abnormal, or aneuploidy, it will not implant, but occasionally it might result in miscarriage. 

Even when a couple does everything right, they simply cannot control which sperm and which egg meet — which, again, is why it’s so important to support the health of our eggs and sperm throughout our reproductive years.