Most Appropriate Investigation Before Prescribing Contraception for AUB
The most appropriate initial investigation is transvaginal ultrasound (with transabdominal ultrasound if needed), as this is the first-line imaging study recommended to identify structural causes of abnormal uterine bleeding before initiating contraceptive therapy. 1, 2, 3
Rationale for Ultrasound as First-Line Investigation
Combined transabdominal and transvaginal ultrasound with Doppler is the most appropriate initial imaging study for identifying structural causes of AUB, including polyps, adenomyosis, leiomyomas, and endometrial hyperplasia/malignancy. 1, 2, 3 This imaging approach is critical before prescribing contraception because:
- Transvaginal ultrasound serves as the primary modality for evaluating the endometrium and myometrium, providing superior visualization compared to transabdominal approaches alone. 2
- Structural causes (polyps, adenomyosis, leiomyomas) are common in premenopausal women with AUB and may influence contraceptive choice or require specific management. 1, 4
- Ultrasound can identify pathology that might contraindicate certain contraceptive methods or require treatment before contraception initiation. 4, 5
Why Other Options Are Less Appropriate
TSH Testing (Option B)
While thyroid-stimulating hormone (TSH) levels should be checked as part of the standard diagnostic workup for AUB 2, this laboratory test does not take precedence over imaging when both contraception and structural evaluation are needed. TSH testing addresses non-structural causes (ovulatory dysfunction) but does not visualize the uterus. 2
FSH Testing (Option A)
FSH is not routinely recommended in the initial workup of AUB in reproductive-age women requesting contraception. 2 It may be relevant for perimenopausal assessment but is not the priority investigation before contraceptive prescription.
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, failed medical management). 2 However, this is not the first-line investigation for all women with AUB requesting contraception. The indication for biopsy is risk-stratified, whereas imaging is universally recommended. 2, 6
Clinical Algorithm for Investigation
Perform pregnancy test (β-hCG) first - mandatory in all reproductive-age women with AUB. 2, 3
Conduct physical examination including speculum examination to visualize cervix/vagina and bimanual examination to assess uterine size and adnexal masses. 2, 3
Order transvaginal ultrasound (with transabdominal if needed) as the primary imaging modality. 1, 2, 3
Obtain TSH and prolactin levels as part of laboratory workup to evaluate for ovulatory dysfunction. 2
Consider endometrial biopsy only if the patient has risk factors for endometrial cancer or if ultrasound findings warrant tissue diagnosis. 2, 6
Common Pitfalls to Avoid
- Do not skip pregnancy testing, even if the patient is requesting contraception - pregnancy must always be excluded first. 2, 3
- Do not rely on transabdominal ultrasound alone in sexually active women, as transvaginal approach provides superior endometrial assessment. 2
- Do not perform routine endometrial biopsy in all women with AUB - target this invasive procedure to those with specific risk factors. 2
- Do not prescribe contraception without imaging when structural pathology could be present, as this may delay diagnosis of significant conditions like endometrial cancer or large fibroids. 1, 4
When to Proceed with Advanced Imaging
Saline infusion sonohysterography (SIS) should be performed when initial ultrasound findings are unclear or suggest intracavitary lesions, with sensitivity of 96-100% for uterine and endometrial pathology. 2, 3 SIS can distinguish between leiomyomas and endometrial polyps with 97% accuracy. 2, 7