Do You Ovulate When Pregnant?

JANE FLANAGAN / FERTILITY PREGNANCY

Your menstrual cycle is typically interrupted by pregnancy. This means when you are pregnant, you typically don’t ovulate or menstruate. The body “switches gears”, so to speak, and focuses on developing the growing embryo. 

However, on rare occasions (i.e. undergoing fertility treatment), fertilization and implantation of a second embryo may occur during an ongoing initial pregnancy. 

In this article, we’ll explain the key phases of a menstrual cycle and then look more closely at what happens during ovulation. Then we will dive deeper with simple terms, into current theories surrounding the complex and rare occurrence of superfetation, which by definition is when a woman becomes pregnant during a different ovulatory cycle, while already pregnant.

Your Menstrual Cycle: The Structures and their Phases

Your monthly menstrual cycle can be divided into 3 phases occurring in two different structures at the same time.

Structures:

  • The ovary
  • The uterus

Phases:

The Ovary

  1. Follicular
  2. Ovulation
  3. Luteal

The Uterus

  1. Secretory
  2. Proliferative
  3. Menstruation  

The most commonly referenced menstrual cycle is 28 days. However, the normal range for many adult women of reproductive age is 21-35 days.

Many also experience irregular menstrual cycles, which can be caused by a variety of differing factors. Tracking the menstrual cycle can be helpful in collecting information and detecting any abnormalities or deviations from your normal menstrual baseline.

What Is Ovulation?

In women of reproductive age, the ovary releases a follicle (oocyte) each month, around days 13–15 of a 28-day menstrual cycle. 


After the oocyte is released from the ovary (ovulation), it moves into the fallopian tube. The rupture of the ovarian follicle during ovulation can cause some light spotting, and some can even feel it happen.


Ovulation is controlled by the release of specific hormones like (i.e. luteinizing hormone (LH) from the pituitary gland (also in the brain) at a specific time within the menstrual cycle. The predictability of ovulation can be affected by other hormone levels as well as stressors. 

What Happens After Ovulation?

After ovulation, the oocyte moves through the fallopian tube for 12–24 hours, waiting to be fertilized by sperm. Your sex drive may also increase during ovulation. It’s worth noting that sperm can live inside a female body for up to 5 days, so the window for getting pregnant is longer than just a couple of days. 


If the egg is not fertilized during that time, it disintegrates (breaks down), and menstruation (your period) begins approximately two weeks (14 days) later.

Ovulation and Pregnancy: ‘The Fertile Window’

For those trying to get pregnant and have a baby, knowing when you might be ovulating is important. Your most fertile days ("the fertile window") are the five days leading up to and including ovulation. The fertile window is when you’re most likely to get pregnant. So, having sex during your fertile window gives you the best chance of ensuring the egg is fertilized by sperm, so you become pregnant.

Taking Advantage of the Fertile Window

As previously mentioned, ovulation is a calculated process. Not to mention, the woman's reproductive cycle is just one side of the equation, i.e. knowing when you're likely to get pregnant is only part of the picture. Sperm health is also key in your chances of getting pregnant.

When you ovulate, an egg is released from a mature follicle in your ovary. The ruptured t follicle transforms into a structure known as the corpus luteum, which exists for two weeks post-ovulation.


The corpus luteum releases mainly progesterone which works to maintain the lining of your uterus (the endometrium) in preparation for implantation of a fertilized egg.

When Does Ovulation Happen?

Every person’s cycle is different. Some have longer periods than others. So the timing of ovulation is not always the same in every woman's cycle, and there can also be a normal variation between cycles in the same person.

A normal menstrual cycle in an adult can be anywhere between 21 to 35 days and21 to 45 days in teens. Tracking your menstrual cycle can be extremely helpful in understanding your normal.

How Do You Count Your Menstrual Cycle?

Your menstrual cycle range is counted from the first day of one menstrual period to the first day of the next menstrual period. Typically ovulation is counted backwards and is about 13-15 days before the first day of your menstrual period flow.

When Are Your Most Fertile Days?

If your average menstrual cycle is 28 days and the first day of your cycle is day 1 of your menstrual period, ovulation typically occurs between days 13-15. Thus, you want to have sex every day or every other day, five days before your fertile window (day 13-15) and continue through your fertile window.

If your average menstrual cycle length is 35 days, ovulation typically happens between days 20-22. Therefore, sexual intercourse should begin five days prior to day 20.

Signs of Ovulation

Ovulation often goes completely unnoticed by women. However, when you ovulate, there are some trackable signs.

Ovulation Symptoms

  • Your basal body temperature falls: Your basal body temperature drops a little bit just before the egg is released from your ovary. Then, 24 hours after the egg's release, your body temperature rises, and the temperature stays up for several days.
  • Cervical mucus changes: The changes in your discharge over the course of your menstrual cycle also hold clues about fertility and when you might be ovulating. If your cervical mucus is:
    • Dry, absent, thick, sticky: ovulation is less likely
    • White, creamy: Ovulation may be coming
    • Clear, slippery and stretchy (cervical mucus is an egg white texture): The probability of ovulation and thus conception is highest.
  • Your cervix softens and opens up: As you approach your most fertile time, your cervix softens. This is sometimes known as having a short, high, open, and wet cervix (SHOW) and is a sign of high fertility. 
  • You may experience a slight twinge or cramping: “Mittelschmerz” translates literally as “middle pain” and is the name for the slight twinge or cramp that some women experience during ovulation (when the follicle releases the egg).
  • Spotting: When the ovary releases an egg, a mature follicle ruptures to allow the egg to be released. This may be a cause of spotting for a day or so.

What Usually Happens When You Get Pregnant?

When you get pregnant, a fertilized egg is implanted in your uterine lining (the endometrium) and grows into an embryo.

The corpus luteum produces progesterone to maintain the lining of the uterus (endometrium)  in a way that facilitates implantation and growth for 14 days. If human chorionic gonadotropin (HCG) is produced by the developing placenta, this stimulates the corpus luteum to continue progesterone production, until the placenta itself takes over the production of progesterone.  HCG is detected in urine during a pregnancy test.

Hormonal Changes

The hormonal fluctuations after becoming pregnant are different (and rightfully so!) from your usual menstrual cycle. 

Pregnancy hormones usually “interrupt” the usual menstrual cycle so that the lining can remain intact for the developing embryo.

These hormonal changes help prepare the woman’s body for a developing fetus and a healthy pregnancy).

According to this article in the New York Times, “Ordinarily, the release of eggs [ovulation] ceases once a woman is pregnant, and the hormonal and physical changes of pregnancy work together to prevent another conception.”

There is a Rare Exception: Superfetation

Theoretically, based on pregnancy physiology, it would be impossible or highly unlikely for a woman to ovulate after getting pregnant. 

However, it is speculated that it is possible to overcome the natural physiological barriers to superfetation with advanced reproductive therapies (i.e. fertility medications used to improve chances of pregnancy).

Superfetation is, by definition, what happens when a woman becomes pregnant, during a different ovulatory cycle, while already pregnant. Superfecundation is a similar but different term that refers to the fertilization of two eggs during the same ovulatory period via separate instances of sex (same or differing partners) or artificial insemination during the ovulatory period.

While it’s common to certain animals (e.g., rodents, rabbits, horses, sheep, kangaroos, badgers, and mink), it is rare in humans. 

How Does Superfetation Occur?

Theoretically, in order for superfetation to occur, a series of unlikely events must happen. These include:

  1. Spontaneous ovulation during pregnancy.
  2. Additional sperm would have to be present in the fallopian tube or would have to travel through a pregnant uterus.
  3. The endometrium must be able to accept a second pregnancy.

The first step alone is unlikely to happen because the hormones released during pregnancy typically block future ovulatory cycles. Of the few cases of superfetation reported, the cause of this has usually been that the person was undergoing advanced reproductive therapies, i.e. fertility treatment.

To give you a real sense of how rare this is, according to a 2008 paper published in the European Journal of Obstetrics and Gynaecology, there have only been 10 cases recorded in medical history. 

Other Factors That Can Disrupt Your Menstrual Cycle

Odds are most of us have experienced a late or missed period related to stress at least once.

Your menstrual cycle is a very calculated and hormone-dependent process that can be disrupted by fluctuations in hormone levels due to stress and other causes. 

Though you shouldn’t panic, some of the factors that can disrupt your menstrual cycle can also be cause for medical concern. Here are some examples.

  • Stress & anxiety: Increased stress may trigger many reactions, including stress hormone (cortisol) fluctuations. Increased levels of cortisol in response to stress may cause changes to your health, including irregularities in menstrual bleeding. For some, breakthrough bleeding may be a sign that you're experiencing high levels of emotional stress.
  • Exhaustion: Feeling jet-lagged or suffering from insomnia? Healthy sleep habits are key, and sleep deprivation can impact the regularity of your menstrual cycle.
  • Diet & eating disorders: Nutrition is key for general wellbeing, including reproductive health. People with eating disorders or energy deficiencies due to decreased or inadequate daily caloric intake may find their cycles disrupted.
  • Polycystic ovary syndrome (PCOS): Women with PCOS may have infrequent or prolonged menstrual periods in combination with increased androgen levels (i.e. testosterone). The ovaries may develop numerous tiny follicles due to their inability to mature follicles and ovulate regularly.
  • Uterine fibroids or polyps: Fibroids are benign growths that can cause heavy and irregular bleeding and disrupt your cycle. They can also cause pain and discomfort.
  • Birth control: Hormonal birth control essentially regulates how the uterus bleeds while also preventing pregnancy.
  • Common infections: Infections such as sexually transmitted infections (STIs) and pelvic inflammatory disease (PID) may cause period irregularities. It’s worth noting that most are treatable when diagnosed early. However, some can become serious and impact future fertility if symptoms are ignored, or an asymptomatic infection is undetected.
  • Medications: Certain medications may cause abnormal vaginal bleeding. Your pharmacist should advise you of any side effects of medication.
  • Perimenopause: This is the stage prior to menopause (when periods cease completely) and is usually characterized by irregular menstrual cycles as periods gradually stop. Menopause is diagnosed when there has been an absence of the menstrual cycle for 12 months (1 year).

When to See a Doctor to Have Symptoms Medically Reviewed

If you experience any of the following, it’s worth scheduling a checkup with your doctor for medical advice:

  • Heavy periods with a lot of clotting (especially clots larger than a quarter)
  • Irregular periods outside of the normal menstrual cycle range or a significant deviation from your normal cycle.
  • Spotting between periods with or without abdominal pain or cramping
  • Pain or a burning sensation when peeing
  • Unusual vaginal discharge and/or redness and itchiness

Don't Ignore These Signs and Symptoms

Even if you don’t have any of the above symptoms, always visit the doctor in the following situations:

  • If you think you’re pregnant or are trying to get pregnant: To be administered a pregnancy test and have an ultrasound performed to confirm the intrauterine location of the pregnancy.
  • If you experience inconsistent spotting: That occurs frequently and randomly and may or may not be associated with cramping and/or pain.
  • Bleeding or spotting after unprotected sex: Unprotected sex can put you at risk for STIs and other infections.
  • Post-menopausal vaginal bleeding: You’ve been through menopause, and you experience vaginal bleeding.

Medically reviewed by Dr. Chimsom T. Oleka, M.D, Written by Jane Flanagan — Updated on November 1, 2021.