The ovaries are small, oval-shaped glands in the female reproductive system, located on either side of the uterus. They are central to reproduction, holding and releasing eggs for potential fertilization, and produce hormones like estrogen and progesterone that regulate the menstrual cycle and support pregnancy. Understanding their typical size provides a baseline for recognizing variations that occur naturally or due to certain health conditions.
Average Ovarian Dimensions
Healthy adult ovaries generally have specific dimensions. An average ovary measures approximately 3 to 5 centimeters (cm) in length, 2 to 3 cm in width, and 1 to 2 cm in thickness. This size is often compared to that of an almond. The typical volume for a healthy adult ovary generally ranges from 3 to 6 milliliters (mL). These are average measurements, and slight variations between individuals or even between a woman’s two ovaries are considered normal.
Factors Influencing Ovarian Size
Ovarian size is not static; it changes considerably throughout a woman’s life and during the monthly menstrual cycle. In childhood, ovaries are relatively small, measuring around 1 cm in diameter and weighing approximately 250-350 milligrams (mg) in a newborn girl. As a girl approaches puberty, the ovaries gradually increase in size, preparing for their reproductive function. They reach their maximum size during the reproductive years.
During each menstrual cycle, ovarian size can temporarily increase due to the development of fluid-filled sacs called follicles, which house immature eggs. One follicle typically grows to become dominant, reaching about 18 to 27 millimeters (mm) in diameter just before ovulation. After the mature egg is released during ovulation, the remaining follicular structure transforms into a corpus luteum, which continues to produce hormones and can also temporarily influence ovarian volume. This physiological enlargement is a normal part of the reproductive process.
Age significantly impacts ovarian dimensions, with a noticeable decline in size occurring after the age of 30. Following menopause, when egg production ceases, the ovaries shrink considerably, typically measuring around 2 cm in length. Their volume also decreases significantly, often to less than 2 mL. During pregnancy, ovaries can also become enlarged due to increased production of hormones like estrogen and progesterone.
When Ovarian Size Changes
Significant deviations from typical ovarian size can indicate underlying medical conditions that warrant attention. One common cause of ovarian enlargement is the formation of ovarian cysts, which are fluid-filled sacs that can develop on or within the ovaries. Functional cysts, such as follicular cysts and corpus luteum cysts, are common and often resolve on their own. Follicular cysts can be larger than 2.5 cm, and corpus luteum cysts can reach about 3 cm. Other types of cysts, like dermoid cysts or endometriomas, can also lead to ovarian enlargement. Some cysts, particularly those larger than 10 cm, may require medical intervention.
Polycystic Ovary Syndrome (PCOS) is another condition that frequently causes enlarged ovaries. In PCOS, hormonal imbalances lead to the presence of multiple small follicles, often 2 to 9 mm in diameter, which accumulate in the ovaries and contribute to their increased volume, sometimes exceeding 10 mL. This can disrupt normal ovarian function, leading to irregular periods and challenges with ovulation. While not all individuals with PCOS have enlarged ovaries, it is a common feature.
Ovarian tumors, though less common, can also cause ovaries to become larger than usual. These growths can be benign (non-cancerous) or, in rare cases, malignant (cancerous). The size of a tumor can vary widely, and while larger tumors might be detected more readily, size alone does not determine whether a tumor is cancerous or its stage. Conversely, conditions like Premature Ovarian Insufficiency (POI), where ovaries stop functioning before age 40, can lead to smaller than average, shrunken ovaries due to a diminished egg reserve. Any notable or persistent changes in ovarian size, especially if accompanied by symptoms such as pelvic pain or bloating, should prompt consultation with a healthcare provider for proper diagnosis and management.