Hi, thank you for choosing HCM. During the second half of your menstrual cycle(after 14th day from day1 of menses) you may have a small fluid filled sac known as a corpus luteal cyst. A corpus luteal cyst is known as a functional cyst. This arises as a cyst of the corpus luteum(the empty follicle after ovulation). The corpus luteum releases progesterone until the placenta takes over this function around 12 weeks gestation. It is diagnosed via ultrasound. A corpus luteal cysts is usually not a cause for concern nor does it usually adversely effect the pregnancy or cause miscarriage. Sometimes you may experience a bit of pain or tenderness. Your doctor or midwife may prescribe pelvic rest or pain medications. The most frequent scenario is that the cyst will resolve on its own. But sometimes the cyst may rupture causing pain and even less likely, the cyst could cause the ovary to twist and potentially require surgery.Kindly visit gynaecologitst if you have sudden onset severe pain in lower abdomen. thank you..