Fertility Basics

Some women are unaware of the very basics of fertility. Fundamentals like understanding the menstrual cycle and knowing when the fertile window takes place can influence a couple’s ability to conceive. That’s why it’s important for providers and patients alike to brush up on the nuts and bolts of fertility. 

MENSTRUAL CYCLE OVERVIEW 

First order of business in understanding fertility is to know the ins and outs of the menstrual cycle. The menstrual cycle has four phases—menstrual, follicular, ovulatory, and luteal.  Each phase is important and disruptions in this cycle is the body’s way of expressing imbalance and a need for repair and restoration. 

The first day of the menstrual cycle is the first day of bleeding (not when the bleeding ends). A normal menstrual cycle is considered 24-35 days, and the actual period (bleeding) itself typically lasts 3-7 days. 

If you are actively tracking your cycle, congratulations! You are taking a big step forward in understanding your fertility. To determine your cycle length, call the first day of bleeding “day 1” and continue counting from there. Count the days until you begin bleeding again. The number of days between the start of your first period and the start of the next period is the length of your cycle. 

THE MENSTRUAL PHASE 

Days 1-7 of the menstrual cycle are called the menstrual phase. This is when the uterine lining is shed (bleeding phase). 

THE FOLLICULAR PHASE 

The next phase of the menstrual cycle is called the follicular phase and takes place during days 8-14 of (approximately). During the follicular phase, the dominant follicle in the ovary starts to mature and grow in preparation for ovulation. Estrogen will start to rise in this phase. 

THE OVULATORY PHASE 

The ovulatory phase occurs during days 15-18 of the cycle (approximately). Estrogen will peak under the influence of luteinizing hormone (LH) releasing an egg from the dominant follicle. This is oftentimes accompanied by an increase in libido and energy, and an increase in cervical mucus that is thin, wet, and slippery. 

THE LUTEAL PHASE 

Days 16-28 of the cycle (approximately) are called the luteal phase and is when progesterone levels increase. The rise in progesterone during the second half of the menstrual cycle is a result of the corpus luteum. Once the ovary releases the mature egg at ovulation from the dominant follicle that grew and matured during the follicular phase, the dominant follicle creates the hormone secreting structure known as the corpus luteum. 

Progesterone only surges for 5-8 days of the month during the luteal phase. Estrogen levels drop down from the ovulatory surge but remain higher than during the follicular phase. If pregnancy does not occur, the corpus luteum will start to disintegrate after about 10-14 days and progesterone and estrogen levels drop. This triggers the next period, and the menstrual phase of the cycle starts over again. 

There is an intricate balance and fluctuation of hormones that interplay throughout the cycle and influence fertility. Each phase of the menstrual cycle is necessary for there to be a successful chance at conception. It’s best practice to test hormones between days 19-22 of the menstrual cycle to capture the mid-luteal peak of hormone levels.