The ovaries are a pair of small, oval-shaped organs located in the pelvis on either side of the uterus. They serve a dual function in the female reproductive system, acting as producers of eggs and factories for sex hormones like estrogen and progesterone. The size and volume of the ovaries are important indicators of health, function, and stage of life, reflecting hormonal activity and the reserve of potential eggs. Because the ovaries constantly respond to hormonal signals, their dimensions vary naturally across a person’s lifetime.
Defining Normal Size During Reproductive Years
During the reproductive years, the ovaries reach their maximum size. Medical professionals measure these organs using ultrasound to determine length, width, and thickness, which are then used to calculate the overall volume. A healthy ovary in an adult woman typically measures between 3 to 5 centimeters in length, 1.5 to 3 centimeters in width, and 0.6 to 1.5 centimeters in thickness.
The size is perhaps most accurately described by its volume, which is calculated using a formula that accounts for the organ’s variable, ellipsoid shape. The average volume for a healthy adult ovary generally falls within the range of 5 to 15 cubic centimeters (cc), although this can vary based on individual factors. This measurement range is an indirect assessment of the ovarian reserve, or the remaining supply of eggs available for ovulation.
The size of the ovary is not static, as it naturally fluctuates throughout the menstrual cycle. During the follicular phase, the ovaries tend to be at their largest because of the development of ovarian follicles. One follicle will mature into the dominant follicle, which can grow significantly before releasing the egg. After the egg is released, the remaining structure forms the corpus luteum, which also contributes to the ovary’s size for a short time.
This monthly cycle of growth and regression means that measurements can vary depending on the timing of the assessment. Slight asymmetries are also common, and it is normal for the right ovary to be marginally different in size from the left ovary.
Changes in Ovarian Size Across the Lifespan
The size of the ovaries changes dramatically outside of the fertile period, reflecting major shifts in the body’s hormonal environment. Before puberty, the ovaries are significantly smaller and relatively inactive, often measuring less than 2 centimeters in length. The average volume during this pre-pubertal stage is very low, typically ranging from 0 to 8 milliliters (ml).
As hormonal signals increase during adolescence, the ovaries gradually grow, reaching their maximum average size by the age of 20. However, even during the reproductive years, a subtle decline in ovarian size begins after approximately age 30, with a measurable reduction occurring with each passing decade. This slow shrinkage is related to the natural depletion of the egg reserve over time.
The most significant reduction in size occurs after menopause, the phase when follicular activity and estrogen production permanently cease. Post-menopausal ovaries undergo atrophy, shrinking by 50% or more compared to their reproductive size. The typical length can drop to as low as 1.5 to 2 centimeters, and the mean volume often decreases to around 2.2 cubic centimeters.
Ovarian volume continues to decline progressively in the years following menopause, and the upper limit of what is considered normal for a post-menopausal ovary is approximately 8 to 10 cubic centimeters. This profound reduction in size is a normal physiological process and is a direct consequence of the cessation of monthly hormonal stimulation and egg maturation.
Common Reasons for Ovarian Size Variation
While age and the menstrual cycle account for normal fluctuations, certain conditions can cause the ovaries to deviate significantly from the typical size range. The most frequent cause of temporary enlargement is the development of functional cysts, which are benign, fluid-filled sacs that form as a normal part of the ovulatory process. These include follicular cysts, which form when a dominant follicle fails to rupture and release the egg, often growing larger than 2.5 centimeters.
These functional cysts usually cause a transient increase in ovarian volume and typically resolve on their own within a couple of months. Polycystic Ovary Syndrome (PCOS) is a hormonal condition that leads to chronically enlarged ovaries, often exhibiting a volume greater than 10 cubic centimeters. This enlargement is due to the accumulation of many small, immature follicles that fail to develop properly because of altered hormone levels, such as excess androgens.
An increase in ovarian size also occurs naturally during pregnancy, primarily because the ovaries are stimulated to produce high levels of hormones like progesterone and estrogen to sustain the pregnancy. In some cases, temporary cysts called theca lutein cysts may form due to the presence of elevated human chorionic gonadotropin (hCG) levels.
Pathological conditions, such as noncancerous tumors or, rarely, ovarian cancer, can also cause substantial and sustained ovarian enlargement. These conditions require prompt medical attention.