What is the most appropriate investigation before prescribing contraception in a 41‑year‑old woman with abnormal uterine bleeding?

Transvaginal Ultrasound Before Prescribing Contraception

In a 41-year-old woman with abnormal uterine bleeding requesting contraception, transvaginal ultrasound is the most appropriate initial investigation before prescribing hormonal contraception. This allows you to identify structural causes of bleeding (polyps, fibroids, adenomyosis, endometrial hyperplasia, or malignancy) that may require specific treatment rather than empiric hormonal therapy, and ensures you are not masking a serious underlying pathology with contraceptive hormones. 1, 2

Why Transvaginal Ultrasound First

The American College of Radiology designates transvaginal ultrasound (combined with transabdominal imaging) as the first-line diagnostic test for abnormal uterine bleeding in premenopausal women, assigning it the highest appropriateness rating (7–9) among all imaging modalities. 1, 2 This recommendation reflects strong guideline consensus that structural pathology must be excluded before initiating hormonal therapy. 1, 2

• TVUS reliably distinguishes structural etiologies—including polyps, adenomyosis, leiomyomas, endometrial hyperplasia, and malignancy—from non-structural causes such as ovulatory dysfunction or coagulopathy. 1, 2

• The examination should assess endometrial thickness, texture, echogenicity, and the presence of focal lesions to fully evaluate pelvic structures. 1, 2

• If TVUS provides adequate visualization and shows a normal endometrium without structural abnormalities, hormonal contraception may be prescribed without further imaging. 2

Age-Specific Risk Considerations

At 41 years, this patient is perimenopausal, which creates two critical clinical concerns:

• Anovulatory cycles become increasingly common in this age group, resulting in unopposed estrogen exposure that markedly raises the risk of endometrial hyperplasia and carcinoma. 2

• Women ≥35 years with abnormal uterine bleeding and risk factors for endometrial cancer (obesity, diabetes, hypertension, nulliparity, PCOS, or prolonged anovulation) should undergo endometrial sampling regardless of ultrasound findings. 3, 2

• However, the initial step remains TVUS to guide whether immediate endometrial biopsy is needed or whether hormonal management can proceed safely. 1, 2

When to Proceed Directly to Endometrial Biopsy

If TVUS demonstrates endometrial thickness ≥10 mm in a premenopausal woman with abnormal bleeding, or if focal endometrial lesions are identified, endometrial sampling becomes mandatory before prescribing contraception. 4, 2

• Hysteroscopy with directed biopsy is superior to blind sampling when focal lesions are present, because blind techniques may miss polyps or localized carcinoma. 5, 6, 2

• If TVUS cannot adequately visualize the endometrium due to body habitus, uterine position, or interfering pathology (adenomyosis, large fibroids), proceed directly to endometrial sampling rather than relying on the incomplete scan. 2

Why the Other Options Are Incorrect

FSH (Option A)

• FSH measurement does not address the immediate diagnostic imperative of excluding structural pathology or endometrial malignancy in a woman with abnormal bleeding. 2

• While FSH can confirm menopausal status in older women, it provides no information about the cause of bleeding and does not guide contraceptive safety. 2

TSH (Option B)

• Although thyroid dysfunction can cause ovulatory abnormalities and abnormal bleeding, TSH should be ordered as part of the laboratory evaluation after structural causes are excluded by imaging. 2, 3

• The American College of Obstetricians and Gynecologists recommends ordering TSH and prolactin to assess endocrine causes of ovulatory dysfunction, but this is secondary to ruling out structural pathology. 2

Endometrial Biopsy (Option D)

• Endometrial biopsy is not the first investigation—it is indicated only after TVUS identifies concerning features (thickened endometrium ≥10 mm, focal lesions) or when the patient has high-risk features warranting immediate tissue sampling. 1, 2, 4

• Performing biopsy without prior imaging is unnecessarily invasive and may miss structural lesions (polyps, fibroids) that TVUS would readily identify. 5, 6

Critical Clinical Pitfall

Do not prescribe hormonal contraception to mask abnormal bleeding without first performing TVUS, because you risk suppressing the presenting symptom of endometrial cancer or other serious pathology. 2 The guideline explicitly states that a speculum or bimanual examination is unnecessary before prescribing most contraceptives 1, but this applies only to asymptomatic women—abnormal bleeding mandates structural evaluation. 1, 2

Algorithmic Approach

1. Order transvaginal ultrasound (combined with transabdominal imaging) to measure endometrial thickness and assess for structural lesions. 1, 2

2. If endometrium is normal (<10 mm) and no focal lesions are present, prescribe hormonal contraception and monitor response. 2, 4

3. If endometrium is ≥10 mm or focal lesions are identified, perform endometrial biopsy (hysteroscopy with directed biopsy preferred) before initiating hormonal therapy. 2, 5, 4

4. If TVUS is inadequate or symptoms persist despite normal imaging and hormonal treatment, escalate to saline infusion sonohysterography or hysteroscopy. 2, 6

5. Order TSH and prolactin as adjunctive tests to evaluate endocrine causes of ovulatory dysfunction, but only after structural pathology is excluded. 2, 3