Correct Answer: C. Torsion of fibroid
Torsion of a fibroid is the most likely diagnosis in this clinical scenario. The key discriminating features are: (1) acute onset severe pain without fever, (2) normal WBC count (8000/μL), and (3) second trimester pregnancy (28 weeks). During pregnancy, the uterus enlarges and becomes mobile, increasing the risk of fibroid torsion—particularly subserosal fibroids on a pedicle. Torsion causes acute ischemia and infarction of the fibroid, presenting with sudden-onset colicky or constant abdominal pain, often localized to the side of the fibroid. The absence of fever and normal WBC rule out infection-related complications. Unlike red degeneration (which is more common in the first and second trimester and presents with fever and elevated WBC), torsion presents with acute mechanical pain without systemic inflammatory signs. Torsion is a surgical emergency requiring immediate imaging (ultrasound or MRI) and often necessitates surgical intervention to prevent further ischemia and potential uterine compromise. The clinical presentation of acute pain in a pregnant woman with known fibroids, in the absence of fever and with normal WBC, makes torsion the most likely diagnosis.
Why the other options are wrong
A. Red degeneration of fibroid — Red degeneration is a common complication of fibroids in pregnancy, but it typically presents with fever, elevated WBC, and systemic inflammatory signs. This patient has a normal WBC count (8000/μL) and no fever, making red degeneration unlikely. Red degeneration is more common in the first and second trimester and is managed conservatively with rest and NSAIDs. The acute mechanical nature of pain without systemic signs points away from red degeneration. B. Preterm labor — Preterm labor at 28 weeks would present with regular uterine contractions, cervical changes, and vaginal bleeding or discharge. The clinical presentation here is acute severe pain without mention of contractions or cervical findings. Additionally, preterm labor is not specifically associated with fibroids causing acute pain. The sudden onset and severity of pain, along with the presence of a known fibroid, make a mechanical complication (torsion) more likely than preterm labor. D. None of the above — This option is a distractor. Torsion of a fibroid is a well-recognized obstetric complication, particularly in pregnant women with subserosal fibroids. The clinical presentation—acute pain, normal WBC, no fever, and known fibroid uterus—fits torsion perfectly. Selecting 'None of the above' would miss the correct diagnosis and delay appropriate management, which may require surgical intervention.
High-Yield Facts
- Fibroid torsion in pregnancy presents with acute-onset severe pain without fever or elevated WBC, distinguishing it from red degeneration.
- Subserosal fibroids on a pedicle are at highest risk for torsion, especially during the second and third trimester when uterine enlargement increases mobility.
- Red degeneration (hyaline necrosis) is more common than torsion in pregnancy but presents with fever, elevated WBC, and systemic signs; managed conservatively.
- Torsion requires urgent imaging (ultrasound or MRI) and often surgical intervention to prevent further ischemia and preserve uterine function.
- Normal WBC count in acute abdominal pain in pregnancy with a fibroid uterus strongly suggests mechanical complication (torsion) rather than infection or inflammatory degeneration.
Mnemonics
TORSION vs RED DEGENERATION Torsion = Tachycardia, acute pain, normal WBC (mechanical) | Red = Redness (fever), elevated WBC, systemic signs (inflammatory). Use when differentiating acute fibroid complications in pregnancy. SUBSEROSAL TORSION RISK Subserosal fibroids on Pedicle = Sudden torsion risk. Intramural and submucosal fibroids rarely twist. Remember: pedunculated subserosal = torsion risk in pregnancy.
NBE Trap
NBE pairs acute abdominal pain in pregnancy with fibroids to lure students into selecting red degeneration (the more common complication). The trap is ignoring the normal WBC and absence of fever—these are the discriminating features that exclude red degeneration and point to the mechanical complication of torsion.
Clinical Pearl
In Indian obstetric practice, fibroids are common (prevalence 4–12% in reproductive-age women), and torsion, though less frequent than red degeneration, is a surgical emergency. A pregnant woman presenting with acute pain and a known fibroid uterus should be evaluated urgently with ultrasound; if torsion is suspected, early surgical consultation is critical to prevent uterine necrosis and preserve fertility.
_Reference: DC Dutta's Textbook of Obstetrics, Ch. 18 (Fibroids in Pregnancy); OP Ghai's Essential Obstetrics, Ch. 12 (Complications of Fibroids)_