Whether ovaries swell before a period involves understanding the menstrual cycle. While significant, painful enlargement is not a typical premenstrual symptom, a minor fluctuation in size is a normal and expected part of the monthly cycle. These changes are driven by hormonal shifts and the development of temporary structures within the ovary. The feeling of being “swollen” that many women experience is usually the result of other physiological changes, separate from the ovary itself.
The Biological Answer: Ovarian Changes During the Luteal Phase
The ovary that released an egg undergoes a size increase during the second half of the cycle, known as the luteal phase. This change is directly caused by the transformation of the dominant follicle into a temporary glandular structure. After ovulation, this collapsed follicle reorganizes its cells to form the corpus luteum, a structure responsible for producing high levels of progesterone.
The corpus luteum is highly vascularized and can grow significantly relative to the size of the ovary, often reaching a diameter between two and five centimeters. Peak size reaches the mid-luteal phase, approximately a week before the expected start of menstruation. This temporary structure causes the dominant ovary’s volume to increase in the days leading up to a period.
If fertilization does not occur, the corpus luteum begins to regress. The collapse of this structure and the resulting drop in progesterone production signal the body to shed the uterine lining. Although this structure causes a detectable change in ovarian volume, this normal, functional swelling rarely results in sharp pain or a sensation of swelling that can be felt externally.
Distinguishing Sensation from Actual Swelling
The sensation of pressure or fullness felt before a period often originates outside the ovary as common premenstrual symptoms (PMS). High levels of progesterone produced by the corpus luteum affect smooth muscle tissue throughout the body. This hormonal influence slows down the motility of the gastrointestinal tract, which can lead to gas and constipation.
Progesterone also affects the body’s fluid balance, promoting sodium and water retention. This fluid buildup causes abdominal bloating and heaviness, sometimes leading to a temporary weight fluctuation. These changes are the main contributors to the sensation of swelling often mistaken for ovarian enlargement.
When Ovarian Enlargement Signals a Problem
While normal ovarian size fluctuation is harmless, persistent swelling can indicate a condition requiring medical evaluation. One common cause is an ovarian cyst, a fluid-filled sac. Functional cysts, like the corpus luteum cyst, usually resolve on their own, but if they overgrow, they can cause discomfort.
Pathological cysts, such as endometriomas or dermoid cysts, cause persistent enlargement and pain. These growths can create mechanical pressure against other abdominal tissues. Conditions like Polycystic Ovary Syndrome (PCOS) are also characterized by enlarged ovaries due to numerous small follicles.
The pain associated with problematic ovarian enlargement is distinct from typical menstrual cramps. It may be sharp, intense, or localized to one side of the lower abdomen, often persisting beyond the start of the period. Symptoms like chronic, unrelieved bloating, unexplained weight loss, or difficulty eating should prompt a consultation with a healthcare provider.