Do You Ovulate on the Pill?

illustration of ovulation
Ovulation. Science Picture Co/Getty Images

Understanding when and if you ovulate is important for contraception as well as pregnancy. Most women do not ovulate when they are on the pill. Some women also do not ovulate when using other forms of hormonal birth control. To understand why, you need to know exactly what happens when you ovulate, how often it occurs, and what ovulation actually means.

Many women confuse ovulation with having their periods, PMS, or conception. Knowing when you ovulate is a part of a natural family planning method to avoid pregnancy. It's also important in maximizing your opportunity to get pregnant.

The Basics of Ovulation and Menstruation

To understand when you ovulate, start with the basic definitions:

  • Ovulation: Ovulation refers to the time a mature egg (possibly more) is released from your ovary. At this time, an egg is available to be fertilized by a sperm—this leads to conception.
  • Menstrual Period: Your menstrual period begins on the first day of your next menstrual cycle. Your period occurs as a result of the hormonal changes that take place when an egg has been released, is not fertilized, and dies. These hormones tell your body that no pregnancy has occurred, so your uterus begins to shed its lining to prepare for your next ovulation day.

Who Ovulates?

Having a menstrual period is usually an indication that you have ovulated. Ovulation typically occurs in the middle of your menstrual cycle. So when you have a period, it means that you are beginning your next cycle and have likely ovulated during your previous cycle. This is one area that can get you in trouble.

Many women who have not had a period in a while (due to stress, miscarriage, breastfeeding, having given birth, etc.) use their periods to determine that they are fertile (ovulating) again. But, if you have been having unprotected sex before this time, you could be at risk for pregnancy since you would have ovulated already—before your period resumes.

If you have excessive monthly bleeding, infertility issues, or irregular menstrual cycles, you may or may not be ovulating. If this applies to you, it is important that you try to determine if and when you ovulate. You may need to seek the help of a doctor and have blood tests to confirm if you have ovulated or are ovulating.

Most women’s menstrual cycles last 28 to 35 days. There seems to be very little cycle variability among women between the ages of 20 and 40. But, you may experience considerable cycle variability during the first five to seven years after you first get your period as well as during the last 10 years before menopause (the stopping of your cycle). Typically, your menstrual cycle length peaks at about age 25 to 30 years and then slowly drops—which is why women in their 40s may have somewhat shorter cycles.

Ovulation and the Pill or Hormonal Contraception

If you are reliably using a hormonal contraceptive (especially a combination method that contains both estrogen and progestin) you do not ovulate. The answer to whether you ovulate on the pill is no.

The hormones in the pill and many of these hormonal methods stop you from ovulating—which is what makes them effective birth control methods. Stop the egg from being released equals no egg, nothing for the sperm to fertilize, and no baby.

If you are using the pill or hormonal birth control methods you do not need to try to track ovulation because you do not ovulate. You do not have "more fertile days" in the middle of the month. You are no more at risk for pregnancy then than on any other day of the month. For those of you who use hormonal methods, the risk factors for contraception failure have to do with if you forget to take pills, change your patch, or if your NuvaRing falls out, etc. With these methods, you need to make sure that there are enough hormones in your body to stop you from ovulation. If you miss too many pills (especially during the first week of a pill pack or at the end of Week 3, where you need to have enough hormone built up to protect you against the hormone-free Week 4), you may be at risk for ovulating.

What Happens Up to and After You Ovulate?

Your normal menstrual cycle is a synchronized cycle of hormonal changes that produce a mature egg (oocyte) to be released. Each month, a series of events occur within your body, which is technically divided into the follicular phase and the luteal phase.

The follicular phase starts with the first day of your period (which is considered Day 1 of your cycle):

  • Low estrogen and progesterone levels help your brain produce the gonadotropin-releasing hormone (GnRH).
  • The GnRH will then activate the pituitary gland to release the follicle-stimulating hormone (FSH).
  • FSH triggers your follicle to grow, and as it does, it causes the production of more estrogen.
  • The follicle grows, your uterine walls become thicker (preparing for possible implantation) and your cervical mucus becomes thinner and stretchier.
  • Your estrogen levels increase over the next 10 days and usually peak one day before you ovulate (in a 28-day cycle, this typically occurs on Day 13).
  • This estrogen peak initiates the luteinizing hormone (LH) surge.

After this surge occurs, you are now in the luteal phase of your cycle:

  • The increased levels of LH cue the ovarian follicle, and you will ovulate about 24 to 36 hours later.
  • Once you ovulate (the egg is released), it leaves behind the corpus luteum (the empty follicle).
  • Progesterone released from the corpus luteum after you ovulate will cause a rise in basal body temperature (your temperature when you're fully at rest) of 0.5 F.
  • If the egg is not fertilized, your LH levels begin to decline and cause the corpus luteum to begin to shrink and produce less progesterone and estrogen.
  • These low hormone levels cause your body temperature to lower, signal your brain to start the whole cycle over again and trigger the uterine lining to shed—thus begins your next period.

This first half of your cycle (the follicular stage) can differ greatly for each woman, usually lasting between 14 and 21 days. The second half of your cycle (the luteal phase) typically has a more precise timeline—beginning on the day you ovulate and usually lasting 14 days. It usually does not vary by more than a day in each person.

What Happens the Day You Ovulate

To determine when you ovulate, you need to count 15 days back from the first day of your period. This is most likely when your LH surge has occurred. Then you can assume that you would have ovulated 1 1/2 days (24 to 36 hours) later. For a 28-day cycle, this would be sometime on Day 14 or 15 (depending on the time the LH surge occurs). To calculate when you will ovulate, you need to:

  • Count back from Day 1 of your cycle.
  • Have reliable cycles that last the same number of days each time.
  • Realize that this is not an exact science—many factors, such as stress, illness or disruption of normal routines, can affect or hinder the hormone production required for you to ovulate.
  • Understand that not all women will ovulate the same time every month.
  • Know that not all women ovulate—especially women who have short menstrual cycles (less than 25 days or longer than 35 days).
  • Remember—you do not ovulate on the pill (or on many forms of hormonal birth control).
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