In a 41-year-old woman with six months of abnormal uterine bleeding who desires contraception, what is the most important investigation to perform before prescribing contraception?

Most Important Investigation: Endometrial Biopsy

In a 41-year-old perimenopausal woman with six months of abnormal uterine bleeding requesting contraception, endometrial biopsy is the most critical investigation before prescribing hormonal contraception, as you must exclude endometrial hyperplasia or malignancy before initiating hormonal treatment that could mask or delay diagnosis of these conditions. 1

Why Endometrial Biopsy Takes Priority

• The American College of Obstetricians and Gynecologists explicitly states that pelvic examination is not necessary before prescribing oral contraceptives for asymptomatic patients, but this does NOT apply to patients with persistent abnormal bleeding, who require evaluation to rule out malignancy before hormonal treatment. 1

• At age 41, this patient is perimenopausal, placing her at increased risk for endometrial pathology including hyperplasia and malignancy. 2

• Six months of abnormal bleeding represents persistent symptoms requiring investigation before masking the problem with hormonal contraception. 1

• Endometrial biopsy is indicated when risk factors for endometrial cancer are present or when medical management is being considered, as it is less invasive, safer, and lower cost compared to dilation and curettage. 3, 1

The Algorithmic Approach

Step 1: Rule Out Pregnancy First

• Pregnancy test (β-hCG) is mandatory in all reproductive-age women with abnormal uterine bleeding before any intervention. 4, 1, 2

Step 2: Perform Endometrial Biopsy

• This is your most important investigation before prescribing contraception because you cannot initiate hormonal treatment without excluding endometrial pathology. 1
• The sensitivity of endometrial biopsy can be affected by various factors including lesion location, but it remains the preferred diagnostic method. 3

Step 3: Consider Ultrasound Concurrently

• Combined transabdominal and transvaginal ultrasound with Doppler should be performed to identify structural causes (polyps, adenomyosis, leiomyomas, endometrial hyperplasia/malignancy). 4, 1, 2
• However, ultrasound alone is insufficient before prescribing contraception in a patient with persistent bleeding, as it may miss focal lesions that endometrial biopsy can detect. 3

Step 4: Check TSH and Prolactin

• TSH and prolactin levels should be checked as part of the diagnostic workup for ovulatory dysfunction. 4, 1, 2
• These are important but secondary to excluding endometrial pathology before hormonal treatment. 1

Why the Other Options Are Insufficient

FSH (Option A)

• FSH is not part of the standard diagnostic workup for abnormal uterine bleeding in guidelines. 3, 4, 1, 2
• It does not help exclude malignancy before prescribing contraception.

TSH (Option B)

• While TSH should be checked as part of the workup for ovulatory dysfunction, it is not the MOST important investigation before prescribing contraception. 4, 1, 2
• Thyroid dysfunction does not preclude safe contraception use, but undiagnosed endometrial pathology does. 1

Ultrasound (Option C)

• Ultrasound is excellent for identifying structural causes and is first-line imaging. 4, 1, 2, 5
• However, in perimenopausal women with persistent bleeding who need contraception, ultrasound alone can miss focal lesions that endometrial biopsy would detect. 3
• The critical distinction is that you cannot safely prescribe hormonal contraception without tissue diagnosis to exclude hyperplasia or malignancy. 1

Critical Pitfalls to Avoid

• Never prescribe hormonal contraception to mask abnormal bleeding without first excluding endometrial pathology in a perimenopausal woman with persistent symptoms. 1

• Do not rely solely on ultrasound findings, as endometrial biopsy is less invasive and safer than dilation and curettage, and can detect focal lesions missed by imaging. 3

• Do not skip pregnancy testing even in perimenopausal women—it remains mandatory. 4, 2

• Recognize that the guideline stating pelvic examination is unnecessary before contraception applies only to asymptomatic patients, not those with six months of abnormal bleeding. 1

When Endometrial Biopsy Can Be Deferred

• If ultrasound shows endometrial thickness <4 mm in a perimenopausal woman, this has nearly 100% negative predictive value for cancer. 2
• However, given six months of persistent bleeding and the request for contraception (which will alter bleeding patterns), tissue diagnosis provides the most definitive exclusion of pathology before treatment. 1