(LUF) Occurs when a reasonably mature tertiary follicle (or preovulatory follicle) receives an LH surge that's enough to make it start producing progesterone, but is not enough to cause it to release its egg through ovulation. The result is that the egg is trapped in the follicle, which to a greater or lesser extent then functions like a corpus luteum, though this stage of the follicle's life is often shorter, giving rise to a luteal phase defect (LPD).

(LPD) A luteal phase that is shorter than optimal for a fertilised egg to undergo implantation. Very likely if the luteal phase is shorter than normal (11 to 16 days), but not all luteal phases within this range are innocent. Often caused by a prior defect of the follicular phase or of the development of the ovulating tertiary follicle (the preovulatory follicle) and hence there can be a defect of the egg itself (if ovulation has actually occurred) or there can be a luteinised unruptured follicle -- any of which will either increase the risk of miscarriage or will prevent pregnancy altogether for that cycle. Synonymous with luteal phase insufficiency.

Nonsteroidal anti-inflammatory drugs, e.g. aspirin, ibuprofen (Advil, Nurofen etc), mefanamic acid (Ponstan), naproxen sodium (Aleve, Naprosyn, or in Naprogesic in combination with dextropropoxyphene), which stop the production of prostaglandins; useful for dysmenorrhea and prior to a hysterosalpingogram. Excessive use at the time of ovulation might predispose to a luteinised unruptured follicle, so NSAIDs should not be used for ovulation pain if you are trying to get pregnant.

A mild pain that precedes ovulation by about 12 hours, felt in the left or right side, but not by everyone or in every ovarian cycle. A good indication of ovulation if it is felt. Can be exaggerated in endometriosis and in so-called pelvic congestion. The time from ovulation pain until the onset of menstruation (ignoring for this purpose any premenstrual spotting) is a good measure of the length of the luteal phase. Should not be treated with NSAIDs such as Advil or Nurofen if you are trying to get pregnant, because these analgesics have been linked to the so-called luteinised unruptured follicle syndrome, or LUF.