**Core Concept**
Clomiphene citrate is a medication used to treat infertility in women, primarily by stimulating the release of hormones that cause ovulation. However, one of the potential side effects of clomiphene citrate is the overstimulation of the ovaries, leading to an excessive release of hormones and fluid accumulation in the abdominal cavity.

**Why the Correct Answer is Right**
Hyperstimulation syndrome (HSS) is a known complication of ovulation induction with clomiphene citrate. It occurs when the ovaries become overstimulated, leading to an excessive release of estrogen and fluid accumulation in the abdominal cavity. This can cause severe abdominal pain, distension, and ascites. The mechanism involves the overproduction of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which stimulates the growth of multiple follicles in the ovaries, leading to an excessive release of estrogen.

**Why Each Wrong Option is Incorrect**
**Option A:** Uterine rupture is a severe complication of pregnancy or labor, but it is not directly related to the use of clomiphene citrate.
**Option B:** Ectopic pregnancy rupture is a life-threatening emergency, but it is not a common complication of clomiphene citrate treatment.
**Option C:** Multifetal pregnancy (twins or triplets) is a possible outcome of ovulation induction with clomiphene citrate, but it does not typically cause sudden onset of abdominal pain and distension.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize the symptoms of hyperstimulation syndrome in patients treated with clomiphene citrate, as it can be a medical emergency requiring prompt treatment. The symptoms include severe abdominal pain, distension, and ascites, and the patient may also experience nausea, vomiting, and diarrhea.

**Correct Answer Line**
✓ Correct Answer: D. Hyperstimulation syndrome