What is the most appropriate initial investigation for a female patient of reproductive age presenting with abnormal uterine bleeding (AUB) and requesting contraception?

Most Appropriate Investigation Before Prescribing Contraception for AUB

In a reproductive-age woman presenting with abnormal uterine bleeding who requests contraception, the most appropriate initial investigation is combined transabdominal and transvaginal ultrasound with Doppler (Option C), preceded by a mandatory pregnancy test. 1, 2

Essential Pre-Investigation Step

• All reproductive-age women with AUB must have a pregnancy test (β-hCG) performed first - this is mandatory before any other investigation or treatment, even in perimenopausal women. 1, 2

Why Ultrasound is the Correct Answer

Combined transabdominal and transvaginal ultrasound with Doppler is the first-line imaging study recommended by the American College of Radiology for identifying structural causes of AUB, including polyps, adenomyosis, leiomyomas, and endometrial hyperplasia/malignancy. 1, 2

• Transvaginal ultrasound serves as the primary modality for evaluating the endometrium and myometrium, while transabdominal imaging assesses larger uteri or masses that exceed the transvaginal field of view. 2
• This imaging approach has high sensitivity and specificity for detecting the common structural causes of AUB in reproductive-age women, including fibroids and adenomyosis. 3
• Ultrasound should be performed before initiating contraceptive treatment to rule out structural pathology that may require different management. 1

Why the Other Options Are Incorrect

TSH (Option B) - Supportive but Not Primary

• TSH levels should be checked as part of the standard diagnostic workup for AUB, but this is a secondary investigation, not the most appropriate initial test. 1, 2
• Thyroid dysfunction is a non-structural cause that can be evaluated alongside imaging, but does not take priority over ruling out structural pathology. 1

FSH (Option A) - Not Routinely Indicated

• FSH testing is not mentioned in any major guideline as a routine investigation for reproductive-age women with AUB requesting contraception. 1, 2, 4
• FSH may be relevant in specific contexts (e.g., suspected premature ovarian insufficiency), but is not part of the standard initial workup. 4

Endometrial Biopsy (Option D) - Only for High-Risk Patients

• Endometrial biopsy should only be performed in reproductive-age women with AUB if additional risk factors for endometrial cancer are present, including obesity, diabetes, hypertension, unopposed estrogen exposure, tamoxifen use, or failed medical management. 2, 4
• All major medical societies (ACOG, NICE, SOGC, FIGO) agree that routine endometrial biopsy is not indicated in reproductive-age women without these risk factors. 4
• Endometrial biopsy alone has variable sensitivity and should not be used to rule out focal lesions. 5

Clinical Algorithm for This Patient

1. Perform pregnancy test (β-hCG) - mandatory first step 1, 2
2. Order combined transabdominal and transvaginal ultrasound with Doppler - identifies structural causes 1, 2
3. Check TSH and prolactin levels - evaluates non-structural causes like thyroid dysfunction and hyperprolactinemia 1, 2
4. Assess for hemodynamic stability - urgent evaluation needed if bleeding saturates a large pad hourly for ≥4 hours 1, 2
5. Perform speculum and bimanual examination - excludes cervical/vaginal sources and assesses uterine size 2

Common Pitfalls to Avoid

• Do not skip pregnancy testing even in women who report using contraception or have irregular cycles - pregnancy must always be excluded first. 2
• Do not perform routine endometrial biopsy in reproductive-age women without risk factors for endometrial cancer - this is unnecessary and not guideline-recommended. 2, 4
• Do not rely on transabdominal ultrasound alone - the transvaginal approach provides superior endometrial assessment and should be combined with transabdominal imaging. 2
• Do not initiate contraception without imaging if structural pathology is suspected, as this may mask underlying conditions requiring different management. 1

When to Consider Advanced Imaging

• Saline infusion sonohysterography (SIS) should be performed if initial ultrasound findings are unclear or suggest intracavitary lesions, with 96-100% sensitivity and 94-100% negative predictive value for uterine pathology. 2
• MRI pelvis should be considered when ultrasound incompletely visualizes the uterus or findings are indeterminate. 1