Women have two ovaries which are located on either side of the uterus. They’re around 3-5 cm long – about the size and shape of an almond. But don’t let their small size fool you! These little organs are pretty powerful. They’re responsible for producing eggs and reproductive hormones, so they hold the key to female fertility and reproduction. In this article, we walk you through 6 facts about ovaries you may not have heard before.
A baby is born with all of the eggs she will have in her lifetime.
When a baby girl is just a tiny fetus in the womb, she has about 6 million eggs. By the time a baby is born, she has between 1-2 million eggs, and she won’t be producing any more. We’re born with a fixed number of eggs that gradually decrease with age.
In the years before puberty, girls lose around 11,000 eggs each month. So by the time you start your first period, there are about 300,000-400,000 eggs left. When the ovaries stop releasing eggs and menstruation stops, you start menopause. When exactly this happens will depend on how many eggs you’re born with and how quickly you lose them, but in the U.S. the average age to begin menopause is 51.
Estrogen and progesterone are produced in the ovaries.
A major function of the ovaries is the production and secretion of the sex hormone groups estrogen and progesterone. These hormones are also made in small amounts in the adrenal glands (and fat cells for estrogen), but the majority come from the ovaries. These hormones play a vital role in the menstrual cycle and female fertility.
At the beginning of the cycle, the ovaries produce and release lots of estrogen, which signals eggs to mature and one gets released during ovulation. After ovulation occurs, progesterone levels rise, which triggers the uterine lining to thicken to get ready for pregnancy. Once you run out of eggs, the ovaries will stop making estrogen and menopause begins.
If a woman has low progesterone levels, it can cause irregular menstrual cycles and fertility problems, because these hormones are crucial to preparing the womb for pregnancy as well as maintaining the pregnancy.
You lose about 1,000 eggs per menstrual cycle, but only one egg is ovulated (usually).
Estrogen triggers the ovaries to mature eggs, and hundreds begin to mature at once. As the days pass, one egg will become the dominant one, and that’s the one that gets ovulated, dropping from the ovaries through the fallopian tubes and into the uterus.
Sometimes, more than one egg gets released during ovulation, which is known as “hyperovulation”. If multiple eggs get fertilized by sperm, you can get pregnant with twins, triplets, or quadruplets. Eggs that don’t get ovulated break down (AKA they die) and get reabsorbed by the body.
Your lifestyle affects ovarian function.
Lifestyle plays a big role in how your ovaries work and fertility in general. In women who have a BMI that’s too high or too low, the ovaries can actually stop working, leading to ovulation problems and trouble conceiving. Over-exercising and high stress levels can also impact the ovaries.
To improve your fertility naturally, try to get to a healthy BMI (between 18.5 and 24.9) and quit smoking if you’re a cigarette smoker. Many scientific studies show that tobacco consumption hurts ovarian function, makes menopause start sooner, and worsens results in assisted reproduction treatments.
Clownfish can choose to change their sex by maturing the ovaries.
Bet you didn’t know this one! Fun fact: all clownfish are actually born male. And they can decide to become female if they want to. How crazy is that?
Here’s how it works: they’re born with both a pair of mature testes and a pair of immature ovaries. If the alpha female in a school of fish dies, one of the males will choose to become the new top dog. Their brain will send messages to the ovaries that it’s time to develop, reorganizing the sex organ tissue and completing their sex transition.
Egg quality decreases as you age.
Not only do our eggs decrease in quantity as we age, but the quality goes down too. According to the American College of Obstetricians and Gynecologists, older women’s eggs are more prone to having abnormal chromosomes. Chromosomal defects are the main cause of miscarriage. They can also lead to birth defects and health conditions such as Down syndrome (trisomy 21).
Because female fertility starts to decline more rapidly in the mid-thirties, women are recommended to seek medical help if they haven’t been able to conceive after six months of regular unprotected sex after age 35, or after one year if you’re under the age of 35.
If you’re struggling to conceive and want to find out why, you can test your fertility with LEVY. Our platform and doctors will take a close look at your reproductive health and recommend which tests you need so we can make a comprehensive fertility analysis. Within just a few weeks, you’ll have a solid understanding of why you haven’t been able to get pregnant and a personalized action plan to help you start your family. Read more about how it works and start decoding your fertility today!
Van Voorhis BJ et al.: The effects of smoking on ovarian function and fertility during assisted reproduction cycles. Obstet Gynecol. 1996;88(5):785-791.
Casas L et al.: Sex Change in Clownfish: Molecular Insights from Transcriptome Analysis. Sci Rep. 2016;6:35461.
Silber S: Unifying theory of adult resting follicle recruitment and fetal oocyte arrest. Reproductive BioMedicine Online. 2015;31(4):472-475.
Women, How Good Are Your Eggs? Yale Medicine. Accessed 07 April 2022.
Having a Baby After Age 35: How Aging Affects Fertility and Pregnancy. The American College of Obstetricians and Gynecologists. Accessed 07 April 2022.
Reproductive Hormones. Endocrine Society. Accessed 07 April 2022.
Chura LR & Norman RJ: Impact of Lifestyle Factors on Ovarian Function and Reproductive Health in Women. SAGE Journals. 2007:511-513.
Normal Ovarian Function. Rogel Cancer Center at the University of Michigan Health. Accessed 07 April 2022.
Normal Ovary. Mayo Clinic. Accessed 07 April 2022.
Ovary. National Cancer Institute. Accessed 07 April 2022.
An Overview of the Ovaries. Endocrine Web. Accessed 07 April 2022.
Estrogen’s Effects on the Female Body. Johns Hopkins Medicine. Accessed 07 April 2022.
BMI for Women: How It Works and What It Reveals About Your Health. Cleveland Clinic. Accessed 07 April 2022.
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