What is the corpus luteum?

Under normal circumstances, there is a small amount of bleeding within the corpus luteum. However, if bleeding becomes excessive, it may increase intraluteal pressure, leading to spontaneous rupture. Some researchers suggest that during vascular luteinization—when luteal blood vessels are functionally immature—capillary bleeding within the corpus luteum is more likely to occur, thereby triggering its rupture. Additionally, conditions such as pelvic inflammatory disease, ovarian congestion, or coagulation disorders may also predispose to spontaneous corpus luteum rupture. But what exactly is the “corpus luteum”? The following section addresses this question.

What Is the Corpus Luteum?

Typically, after each ovulation, a corpus luteum forms in the ovary. During pregnancy, the corpus luteum enlarges and secretes hormones that thicken the endometrium, suppress uterine contractions, and promote mammary gland secretion. The luteal phase refers to the period from ovulation until the day before menstruation begins—usually lasting approximately 14 days. For example, in a 28-day menstrual cycle, the luteal phase corresponds to days 15–28. Furthermore, after ovulation, under the influence of luteinizing hormone (LH), ovarian granulosa and theca cells undergo further proliferation and differentiation. Their cytoplasm accumulates yellow pigment granules and lipid droplets, giving the structure a yellowish appearance to the naked eye—hence the name “corpus luteum” (Latin for “yellow body”). The development and fate of the corpus luteum depend on whether the ovulated oocyte is fertilized: if fertilization does not occur, the corpus luteum degenerates after about 14 days, resulting in menstrual shedding; if fertilization occurs, the corpus luteum persists until the end of the third month of pregnancy before gradually regressing. This distinction is clinically important.

Knowledge Extension: Clinical Manifestations of Corpus Luteum Rupture

1. Vaginal Bleeding

Corpus luteum rupture most commonly occurs during the second half of the menstrual cycle. Typically, patients do not experience amenorrhea or vaginal bleeding. Pregnancy tests usually yield negative results. Therefore, in cases of acute abdominal pain due to intra-abdominal hemorrhage in gynecologic patients—especially when no amenorrhea or vaginal bleeding is present and the pregnancy test is negative—spontaneous corpus luteum rupture should be strongly considered.

2. Lower Abdominal Pain

Patients often experience sudden onset of lower abdominal pain during the latter half of the menstrual cycle, accompanied by tenderness and rebound tenderness in the lower abdomen. Gynecological examination may reveal cul-de-sac (posterior fornix) tenderness and cervical motion tenderness (cervical lift pain), along with a tender adnexal mass on one side. Transvaginal ultrasound typically shows pelvic fluid accumulation and an adnexal mass; culdocentesis yields non-clotting blood. Because its clinical presentation, physical signs, and ultrasound findings closely resemble those of ectopic pregnancy, differential diagnosis is essential.

3. Nausea and Vomiting

Many patients also experience nausea and vomiting. This condition may affect both married and unmarried women, but is most common among women of childbearing age. In a minority of cases, abdominal pain occurs around mid-cycle or approximately one week after menstruation, sometimes accompanied by mild vaginal bleeding—these are relatively common manifestations of corpus luteum rupture.

The above provides an overview of what the corpus luteum is. We hope this information is helpful to you.