PLAB PLAB Obstetrics & Gynecology 2 — Questions and Answers
Question 1: A 45-year-old woman presents with heavy menstrual bleeding, pelvic pressure, and urinary frequency. Pelvic examination reveals an enlarged, irregular uterus. What is the most likely diagnosis?
- Endometriosis
- Uterine fibroids (leiomyomas) (Correct answer)
- Endometrial carcinoma
- Adenomyosis
Correct answer: Uterine fibroids (leiomyomas)
Uterine fibroids (leiomyomas) are benign smooth muscle tumors causing uterine enlargement with irregular contour, heavy menstrual bleeding, and bulk symptoms such as pelvic pressure and urinary frequency.
Question 2: Which hormone is measured in a serum pregnancy test, and at what level does a transvaginal ultrasound typically visualize an intrauterine gestational sac?
- Progesterone; >500 mIU/mL
- hCG; >1500–2000 mIU/mL (Correct answer)
- LH; >25 IU/L
- Estradiol; >200 pg/mL
Correct answer: hCG; >1500–2000 mIU/mL
Human chorionic gonadotropin (hCG) is produced by the syncytiotrophoblast after implantation, and a transvaginal ultrasound can typically identify an intrauterine gestational sac when hCG exceeds 1500–2000 mIU/mL (the discriminatory zone).
Question 3: A 50-year-old postmenopausal woman presents with vaginal bleeding. What is the most important first investigation?
- Pap smear
- Endometrial biopsy (Correct answer)
- Pelvic MRI
- Serum CA-125
Correct answer: Endometrial biopsy
Postmenopausal bleeding must be evaluated with endometrial biopsy (or transvaginal ultrasound measuring endometrial thickness) to exclude endometrial carcinoma, which is the most concerning cause.
Question 4: Which condition is characterized by endometrial glands and stroma found within the myometrium, causing dysmenorrhea and a uniformly enlarged uterus?
- Endometriosis
- Adenomyosis (Correct answer)
- Uterine fibroids
- Endometrial hyperplasia
Correct answer: Adenomyosis
Adenomyosis is defined by ectopic endometrial glands and stroma embedded within the myometrium, resulting in a symmetrically enlarged, globular uterus and severe dysmenorrhea with heavy menstrual bleeding.
Question 5: What is the mechanism of action of combined oral contraceptive pills (COCPs) in preventing pregnancy?
- Thickening cervical mucus only
- Inhibiting ovulation via suppression of LH and FSH (Correct answer)
- Preventing implantation only
- Inhibiting sperm motility
Correct answer: Inhibiting ovulation via suppression of LH and FSH
COCPs primarily work by suppressing the LH surge and FSH release through negative feedback on the hypothalamic-pituitary axis, thereby inhibiting ovulation; secondary mechanisms include cervical mucus thickening and endometrial changes.
Question 6: A pregnant woman at 26 weeks has a routine glucose challenge test (GCT) result of 165 mg/dL. What is the next step?
- Diagnose gestational diabetes and start insulin
- Perform a 3-hour 100g oral glucose tolerance test (OGTT) (Correct answer)
- Repeat the GCT in 4 weeks
- No further testing needed
Correct answer: Perform a 3-hour 100g oral glucose tolerance test (OGTT)
A GCT result ≥140 mg/dL (some centers use ≥130 mg/dL) is a positive screen that requires confirmation with a diagnostic 3-hour 100g OGTT to diagnose or exclude gestational diabetes mellitus.
PLAB PLAB Obstetrics & Gynecology 2
A 45-year-old woman presents with heavy menstrual bleeding, pelvic pressure, and urinary frequency.
Pelvic examination reveals an enlarged, irregular uterus.
What is the most likely diagnosis?