In a 41‑year‑old woman with abnormal uterine bleeding (AUB) requesting contraception, what is the most appropriate investigation to perform before prescribing contraception?

Investigation Before Prescribing Contraception in a 41-Year-Old Woman with AUB

The most appropriate investigation is transvaginal ultrasound (combined with transabdominal ultrasound when needed), as this is the first-line imaging modality recommended by multiple guidelines to identify structural causes of abnormal uterine bleeding before initiating contraceptive therapy. 1, 2, 3

Rationale for Ultrasound as First-Line Investigation

Transvaginal ultrasound with transabdominal ultrasound serves as the primary diagnostic tool because it can identify structural causes of AUB including polyps, adenomyosis, leiomyomas, and endometrial hyperplasia/malignancy—all of which may influence contraceptive choice or require specific management before contraception is initiated. 1, 2, 3

The American College of Radiology specifically recommends combined transabdominal and transvaginal ultrasound with Doppler as the most appropriate initial imaging study for identifying structural causes of AUB. 4, 3 This approach provides:

• Superior visualization of the endometrium and myometrium through the transvaginal approach 4, 1
• Assessment of larger uterine structures that may extend beyond the transvaginal field of view using the transabdominal approach 4
• High diagnostic accuracy with pooled sensitivity and specificity of 82.5% and 84.6% respectively for adenomyosis, and ability to detect leiomyomas and polyps 4

Why Other Options Are Not First-Line

TSH (Option B)

While TSH should be checked as part of the standard diagnostic workup for AUB to evaluate for ovulatory dysfunction, this laboratory test does not take precedence over imaging when both contraception and structural evaluation are needed. 1, 2 TSH testing addresses non-structural causes but misses the critical structural pathology that ultrasound identifies. 2, 3

FSH (Option A)

FSH is not routinely recommended in the initial workup of AUB in reproductive-age women requesting contraception. 1 It may be relevant for perimenopausal assessment but is not the priority investigation in this 41-year-old woman. 1

Endometrial Biopsy (Option D)

Endometrial biopsy should be performed in perimenopausal women with risk factors for endometrial cancer (obesity, diabetes, hypertension, unopposed estrogen exposure, tamoxifen use, Lynch syndrome), but is not the first-line investigation for all women with AUB requesting contraception. 1, 2 Multiple guidelines agree that endometrial biopsy should only be performed if additional risk factors for endometrial cancer are present, not routinely in all cases of AUB. 5

Clinical Algorithm for This Patient

1. Perform pregnancy test (β-hCG) first—mandatory in all reproductive-age women with AUB 1, 2, 3

2. Conduct physical examination including speculum examination to exclude cervical/vaginal sources and bimanual examination to assess uterine size and adnexal masses 1, 2

3. Order transvaginal ultrasound (with transabdominal if needed) as the primary imaging modality 1, 2, 3

4. Consider TSH and prolactin levels as part of laboratory workup to evaluate for ovulatory dysfunction 1, 2

5. Reserve endometrial biopsy only if the patient has risk factors for endometrial cancer or if ultrasound findings warrant tissue diagnosis 1, 2

Important Clinical Considerations

Structural causes such as polyps, adenomyosis, and leiomyomas are common in premenopausal women with AUB and may influence contraceptive choice. 1 For example, a levonorgestrel IUD may be therapeutic for adenomyosis or small fibroids, while large structural lesions may require surgical management before or instead of hormonal contraception. 6

A pelvic examination is not required before prescribing most forms of contraception (oral contraceptives, patch, ring, implant, injections), as there is nothing found on examination that would contraindicate these methods. 4 However, investigating the cause of AUB is a separate clinical priority that requires imaging to exclude significant pathology. 1, 5

If initial ultrasound findings are unclear or suggest intracavitary lesions, saline infusion sonohysterography should be performed, with sensitivity of 96-100% for uterine and endometrial pathology. 1, 2