The ovaries are egg-producing glands that are part of the female reproductive system. The ovaries are about the size and shape of an almond, and they sit just above the fallopian tubes—one ovary on each side of the uterus.
In a fertile female, either the right or left ovary produces a mature egg for fertilization every month during ovulation. Typically, a single egg is released at a time, but in some cases, more than one egg can be released, sometimes resulting in the conception of multiples (such as twins or triplets).
Ovarian Follicles
At birth, a female baby has about 1 million ovarian follicles. Each ovarian follicle contains a hollow ball of cells with an immature egg in the center.
During childhood, approximately half of the ovarian follicles are absorbed by the body. By the time of puberty and the beginning of an individual's menstrual cycle, only about 400,000 ovarian follicles are left to develop into mature eggs.
Although only one egg usually fully matures during each ovulation, between 10 and 20 follicles begin the process of maturation monthly. The excess ovarian follicles are reabsorbed before ovulation occurs.
Ovulation
Around the middle of the menstrual cycle (typically day 14 of a 28-day cycle, though this timing may vary), the process of ovulation is initiated.
The steps of ovulation are:
- A decrease in estrogen (mostly estradiol) and secretion of gonadotropin-releasing hormone (GnRH) sends a message to the pituitary gland to increase its secretion of follicle-stimulating hormone (FSH).
- The increase in FSH causes the growth of 10–20 ovarian follicles (immature eggs).
- Estrogen is secreted by some of the cells in the follicle and progesterone is produced by the cells in the ovarian follicles shortly before ovulation occurs.
- Just before ovulation occurs, the follicle that contains the maturing egg eases toward the surface of the ovary.
- Once the matured egg reaches the ovarian surface, ovulation occurs, when the follicle and the ovarian surface open, allowing the egg to drift out of the ovary.
- After the egg is released from the ovary, it travels to the oviducts (the funnel-shaped ends of the fallopian tubes), where it begins its long journey of several days into the uterus.
- The mature egg is moved along on its journey by wavelike muscle contractions in the fallopian tube.
- The inner lining of each fallopian tube contains cilia, which are constantly beating microscopic hairs. These cilia are what help move the sperm toward the egg if a person has had unprotected sexual intercourse.
Conception (the fertilization of an egg with sperm) most often occurs in the part of the fallopian tube that is nearest the ovary. Five to six days are required for the fertilized egg to reach the uterus.
After ovulation, if pregnancy has not occurred, the empty follicle, called the corpus luteum, is reabsorbed into the body. If pregnancy does occur, the corpus luteum produces hormones that help to maintain the pregnancy.
Eggs that are not fertilized either disintegrate or flow out of the body (unnoticed) with vaginal secretions.
Why Do My Ovaries Hurt?
You might experience a twinge, a cramp, or some discomfort in your lower back or abdomen when ovulation occurs. Some people notice a small amount of vaginal discharge, sometimes containing a small amount of blood, during ovulation.
Symptoms during ovulation are called "mittelschmerz," or midcycle pain. For some people, these symptoms are severe enough to be mistaken for an ectopic pregnancy (when a fertilized egg implants outside the uterus) or appendicitis (inflammation of the appendix, on the lower right side of the abdomen). Others experience headaches, gastric pain, or general malaise (overall feeling of not being well), while still others actually feel much better during ovulation.
Mittelschmerz Midcycle Pain
Ovarian Torsion
Rarely, an ovary can twist around the ligament that's holding it in place. This condition is known as ovarian torsion and can result in severe pain. Ovarian torsion is considered a medical emergency because the twisting (torsion) can cut off blood supply to the ovary and fallopian tube.
The initial symptoms are severe pelvic pain, typically on one side, along with nausea and vomiting. Immediate surgery is usually required to restore the blood supply and preserve the ovary. Ovarian torsion may account for up to 3% of all gynecological emergencies.
Ovarian Cysts
Ovarian cysts are fluid-filled sacs similar to blisters that can form on the ovaries. Ovarian cysts are common during the reproductive years. Most types of ovarian cysts are harmless and go away without any treatment.
What Are Ovarian Cysts?
Polycystic Ovary Syndrome
Polycystic ovary syndrome (PCOS) is a hormonal disorder that affects an estimated 7% of all females. It is the most common hormonal disorder among females. According to experts, the actual number of people affected by PCOS may be as high as 1 out of 10.
Many cases of PCOS are undiagnosed because the symptoms can vary from person to person. It also is often difficult to accurately diagnose. Because polycystic ovary syndrome can cause significant long-term health consequences, getting an accurate diagnosis, followed by proper treatment, is important.
How PCOS Is Diagnosed
Ovarian Cancer
Ovarian cancer is often called the "silent killer" because it usually doesn't cause symptoms until the disease has progressed to an advanced stage. In the United States, ovarian cancer ranks fifth in cancer deaths among women, making it the deadliest gynecological cancer.
Ovarian Cancer Symptoms and Causes
Fallopian Tube Damage
Fallopian tubes that have been damaged by diseases, infections, or other conditions may be scarred or damaged, which increases the risk of an ectopic (tubal) pregnancy.
Some of the causes of fallopian tube damage are pelvic inflammatory disease (PID, an infection in the upper reproductive system) or endometriosis (tissue that normally grows inside the uterus develops outside this organ), as well as some sexually transmitted infections (STIs) or other pelvic infections.
Frequently Asked Questions
Is it possible for both ovaries to release an egg in the same cycle?
Yes. Normally, only one egg is released during ovulation, but it is possible for both ovaries to release an egg at the same time. If both those eggs become fertilized, they may result in fraternal (nonidentical) twins.
What happens to ovaries during a hysterectomy?
Hysterectomy is surgical removal of the uterus. In about half of hysterectomies, the ovaries are removed as well, in a procedure known as an oophorectomy. This may be recommended to reduce the risk of ovarian cancer, especially if you are considered of high risk.
Learn More: Oophorectomy: Everything You Need to Know
What causes ovarian cysts?
Ovarian cysts commonly form during ovulation or pregnancy. In some cases, they may result from hormonal treatments, including fertility treatments. Other causes are PCOS, endometriosis, or a pelvic infection.
How do you determine which ovary released the egg in a given cycle?
This is not usually easy to know. The simplest way to determine which ovary released the egg is by paying attention to any slight twinges of pelvic pain that may occur during your ovulation window, known as mittelschmerz. That slight pain on the right side or left side is likely the best indicator of which ovary released the egg.
What happens to ovaries after menopause?
After menopause, the ovaries stop releasing eggs and cease production of the hormone estrogen. However, they will still continue to produce testosterone alongside the adrenal glands. The ovaries become slightly smaller after menopause, but won't disappear.
How do you know which side is ovulating?
Track whether you feel it on the left side, right side, or both. Ovulation pain is typically felt on the side of the ovary that is releasing an egg that cycle; it may be felt in the middle or on the opposite side of ovulation (5).What determines which ovary releases an egg?
Ovulation occurs when one of your follicles matures enough to release an egg and it doesn't matter which side this happens on. Actually, many women find they ovulate from one side more often than the other. An older study from 2000 showed women actually ovulate more on the right ovary than the left (14).Which ovary is more likely to conceive?
Taken together, in both fertile and infertile women the fertility potential of oocytes from the right ovary surpasses that of the left ovary.Can you feel which ovary releases an egg?
You may feel it on the side where the ovary is releasing an egg. (For most people, the ovaries take turns ovulating. Each ovary releases an egg every other month.) So if the ovary on the right side is releasing the egg, that's where you'll feel the pain.