If you want to know which phase you’re on in your menstrual cycle or when your period will be arriving, there’s an easy trick to figuring it out. It works for healthy cycles of any length: 28 days, longer than 28 days, shorter than 28 days, and even cycles that vary in length from month to month. All it takes is pinpointing when you ovulate. That’s because your cycle is split into two “halves”–and ovulation plays a key role in figure out which half you’re in.
This is called the “follicular” phase because a follicle matures in your ovary. This phase starts with the first day of your period (Day 1) and lasts until ovulation.
An important cycle clue to know about your follicular phase: This is the part of your menstrual cycle that varies in length. The first “half” of your cycle determines just how long your whole cycle will be.
This means if you have a menstrual cycle that lasts 28 days, this first “half” of your cycle typically lasts 14 days. So, ovulation would be on Day 14. However, if you have a cycle that’s less than 28 days, this part of your cycle is shorter than 14 days, so your ovulation day will be sooner. (For example, in a 26-day cycle, ovulation day would be on Day 12.) And if you have a cycle that’s longer than 28 days, this part of your cycle is longer than 14 days, so your ovulation day will be later. (For example, in a 30-day cycle, ovulation day would be on Day 16.)
The day after you ovulate, you enter the second half, or “luteal” phase, of your cycle. It gets its name from the hormone progesterone, which is produced by a substance in the ovary that’s left behind after ovulation called the corpus luteum. This phase lasts until the day before your next period.
An important cycle clue to know about your luteal phase: It’s generally a stable set number of days that does not vary in length.
This phase is typically 14 days in most menstrual cycles. That’s because once ovulation occurs, a clock inside your body begins to tick down either to your period or pregnancy. If you didn’t get pregnant, then the clock stops and you go on to get your period. (Note: In some, this phase can be slightly shorter or longer, such as 12 days or 15 days, but the luteal phase still tends to be a stable set number of days from cycle to cycle.)
Thanks to these cycle clues, you can always know where you are in your menstrual cycle:
The above are all general rules. Because the menstrual cycle is impacted by other processes going on in your body, this predictable pattern can be thrown off, for example, by stress, illness or medication. Also, the above applies to healthy menstrual cycles. If you are challenged with a condition that impacts hormones or the menstrual cycle, such as polycystic ovarian syndrome, then naturally these rules would not apply.
Basal thermometer: This special thermometer detects a subtle rise in your body temperature that occurs at ovulation (and throughout your luteal phase) due to elevated progesterone. To use: Take your temperature every day once you wake up, but before you get out of bed. When you notice a rise in temperature of one-half to one degree in the middle of your cycle, it’s a sign that you’re ovulating.
Ovulation microscope: This lipstick-sized reusable microscope measures the amount of salt in your saliva, which peaks shortly after ovulation. To use: Dab a little saliva on the lens, allow to thoroughly dry, then look through the microscope. If you see dots, you’re not near ovulation. If you see dots and lines, you’re nearing ovulation. If you see ferns, you ovulated the day before.
Urine test strips: These disposable strips measure the level of luteinizing hormone (LH) in your urine. The amount of this hormone that your body produces surges one to one-and-a-half days before ovulation. To use: Simply pass the strip through your urine stream. Then, wait for the strip to indicate the level of LH in your system. When it peaks, you’ll be ovulating within 24 to 36 hours.
Important: Please do not use the information about ovulation on this web page as a sole form of pregnancy prevention. If you do not use birth control (such as condoms), you can get pregnant on the days leading up to, the day of and the day after ovulation. That’s because sperm can survive within your body for up to five days and your egg can survive up to 48 hours.
Do you always ovulate on the same day of your cycle, so you’re not worried about birth control on the other days in your cycle? Not so fast: Your usual ovulation date could have shifted due to stress, illness, medication or another factor, which means that even if you tried to calculate your most fertile days, your body could have made other plans, leaving you at risk.
So, please use an effective and safe form of birth control when trying to avoid pregnancy.
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