The ovaries are small, paired reproductive glands that serve as the body’s source of female gametes and sex hormones. Estrogen and progesterone, produced by these organs, regulate the menstrual cycle and support fertility. Ovarian size is not fixed; it changes significantly based on age, hormonal activity, and reproductive status. Evaluating ovarian dimensions is a standard procedure in reproductive medicine, as size often indicates overall reproductive health and potential underlying conditions.
Standard Dimensions During Reproductive Years
The healthy ovary in a woman of reproductive age is typically described using three dimensions and a calculated volume. Measurements are primarily obtained non-invasively through transvaginal or transabdominal ultrasound imaging. On average, a healthy ovary measures approximately 3 to 5 centimeters in length, 1.5 to 3 centimeters in width, and 0.6 to 1.5 centimeters in thickness.
These dimensions translate to an average ovarian volume of about 6 to 7 milliliters (mL) in premenopausal women. Volume is often the most relevant metric because it correlates strongly with the total number of small follicles present. While a volume up to 14 to 15 mL may be considered normal for younger women, any significant deviation from the average prompts further investigation.
Normal Size Variations Across the Lifespan
Ovarian size is closely tied to a woman’s age and hormonal environment, changing significantly from birth to post-menopause. In the pre-pubertal phase, the ovaries are small and largely inactive, often having a volume less than 1 mL. Size begins to increase gradually as puberty approaches, reflecting the slow growth of the internal stroma.
The surge in reproductive hormones during adolescence causes a significant increase in size, peaking around age 20. Following this peak, a steady, decades-long decline in ovarian volume begins, linked to the continuous depletion of the ovarian follicle reserve.
The most dramatic size change occurs following menopause, when the cessation of follicular activity leads to ovarian atrophy. Post-menopausal ovaries are typically half the size or less of those in reproductive years, dropping to a mean volume of about 2.8 mL at menopause and further decreasing to around 2.1 mL in women over 60.
Cyclical Changes Driven by the Menstrual Cycle
The ovaries exhibit temporary fluctuations in size over the course of the menstrual cycle. During the follicular phase, a cohort of follicles begins to mature, but typically only one, the dominant follicle, continues to grow. This dominant structure can reach a diameter of 22 to 24 millimeters just before ovulation, significantly increasing the overall volume of that specific ovary.
Following the release of the egg, the remnants of the ruptured follicle transform into the corpus luteum, a temporary endocrine structure that produces progesterone. This structure occupies space and contributes to the enlarged size of the ovary during the luteal phase. The corpus luteum can measure between 2 and 5 centimeters, causing the dominant ovary’s volume to increase again, sometimes exceeding its pre-ovulatory size.
The non-dominant ovary, which did not release an egg, generally remains stable in size throughout the cycle. This temporary difference explains why one ovary may be up to twice the volume of the other during the month.
Conditions That Cause Abnormal Size
Several medical conditions can cause the ovaries to deviate significantly from their normal size, most commonly resulting in enlargement. Ovarian cysts are a frequent cause, where fluid-filled sacs form on or inside the ovary. Functional cysts, such as follicular or corpus luteum cysts, are usually temporary, but pathological cysts, like endometriomas or dermoid cysts, can persist and grow large.
Polycystic Ovary Syndrome (PCOS) is another common cause of ovarian enlargement, characterized by numerous small, immature follicles accumulating in the ovaries. This morphology results in a distinct ultrasound appearance and increased ovarian volume. Additionally, the presence of benign or malignant masses, such as tumors or cystadenomas, can cause severe and sustained enlargement, which is a serious medical concern.
Conversely, a smaller-than-expected ovarian size in a young woman may indicate diminished ovarian reserve or premature ovarian insufficiency (POI). In POI, the ovaries stop functioning normally before age 40, leading to follicle depletion and subsequent shrinkage, mimicking post-menopausal atrophy.