**Core Concept:** Clomiphene citrate is a selective estrogen receptor modulator (SERM) used for ovulation induction in women with anovulation or oligoovulation due to hypothalamic-pituitary disorders. It competes with estrogen at the estrogen receptor, thereby increasing luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels, which leads to ovulation.

**Why the Correct Answer is Right:** The most serious complication of clomiphene citrate therapy is Ovarian Hyperstimulation Syndrome (OHSS). OHSS is a potentially life-threatening complication that occurs due to excessive stimulation of the ovaries, leading to large follicle growth, ovarian edema, and accumulation of ascitic fluid. It can be mild, moderate, or severe, with severe cases requiring hospitalization and monitoring.

**Why Each Wrong Option is Incorrect:**

A. Ovarian Rupture: Although clomiphene citrate increases the risk of multiple follicle growth, it does not specifically increase the risk of ovarian rupture.
B. Ectopic Pregnancy: While clomiphene citrate may increase the risk of multiple pregnancies, the risk of ectopic pregnancy is not directly linked to its use.
C. Polycystic Ovarian Syndrome (PCOS): This option is incorrect because PCOS is a condition characterized by hormonal imbalance and polycystic ovaries, which is unrelated to clomiphene citrate therapy.
D. Ovarian Torsion: Although clomiphene citrate can lead to multiple follicle growth, there is no direct link between its use and ovarian torsion.

**Clinical Pearl:** Ovulation induction with clomiphene citrate must be carefully monitored, especially in high-risk patients, to prevent OHSS and its complications. An appropriate monitoring protocol involves monitoring the patient's ultrasound examination and serum beta-human chorionic gonadotropin levels. If OHSS is suspected or confirmed, clomiphene citrate administration should be stopped, and supportive care is initiated for the patient.