What is the optimal timing for a transvaginal ultrasound (US) in infertility evaluation?

Optimal Timing for Transvaginal Ultrasound in Infertility Evaluation

Transvaginal ultrasound (TVUS) for infertility evaluation should be performed during the early follicular phase, specifically on cycle days 5-9, as this timing provides optimal visualization of baseline ovarian reserve, antral follicle counts, endometrial cavity anatomy, and allows for comprehensive assessment of pelvic structures in a single visit. 1

Rationale for Early Follicular Phase Timing

The early follicular phase (days 5-9) is ideal because:

• Antral follicle counts are most accurately assessed when follicles are at their baseline size before dominant follicle selection, providing reliable evaluation of ovarian reserve 2
• The endometrium is thin, allowing superior visualization of the endometrial cavity, polyps, submucosal fibroids, and müllerian anomalies without interference from proliferative changes 1
• A comprehensive "one-stop shop" evaluation can be performed, including assessment of uterine anatomy, ovarian morphology, tubal patency (via sonohysterography/HyCoSy), and adnexal structures in a single visit 1

Specific Assessment Components by Timing

Ovarian Reserve and PCOS Evaluation

• TVUS during early follicular phase allows measurement of antral follicle counts and ovarian volume to assess diminished ovarian reserve (defined as <5 antral follicles and ovarian volume <3 cm³) 2
• For polycystic ovary syndrome (PCOS) diagnosis, TVUS identifies polycystic ovarian morphology using updated thresholds of ≥25 follicles or ovarian volume ≥10 mL 2

Uterine Cavity Assessment

• Two-dimensional and three-dimensional TVUS during days 5-9 evaluates endometrial cavity shape, müllerian duct anomalies, fibroids, adenomyosis, and polyps with optimal clarity 1
• Sonohysterography (saline infusion sonography) can be performed during this same visit for detailed endometrial cavity evaluation and tubal patency assessment 3, 1

Important Clinical Caveats

Avoid Common Pitfalls

• Do not perform TVUS during the luteal phase for initial infertility evaluation, as the thickened endometrium obscures cavity lesions and follicle assessment is less accurate 1
• Transabdominal ultrasound alone is insufficient for infertility evaluation; it should only be used if TVUS cannot be performed, as it provides inferior visualization of ovarian follicles and endometrial detail 2

When Alternative Timing May Be Considered

• For monitoring follicle development during ovulation induction, serial TVUS throughout the cycle is necessary 2
• If evaluating for endometrial polyps specifically in women with abnormal uterine bleeding, days 11-13 of the follicular phase may provide optimal sensitivity (82.5%) and specificity (73%) 4

Comprehensive Single-Visit Protocol

The modern infertility TVUS examination on cycle days 5-9 should include:

• Grayscale assessment of endometrial thickness, cavity contour, myometrial texture, junctional zone, and adnexal structures 1
• Antral follicle count in both ovaries and ovarian volume measurement 2
• Doppler evaluation of ovarian stromal blood flow if PCOS is suspected (though routine Doppler is not required) 2
• Assessment of organ mobility by gentle pressure to detect adhesions or endometriosis 1
• Sonohysterography with tubal patency assessment (HyCoSy) using air-saline or contrast to evaluate tubes in real-time 1

This timing strategy maximizes diagnostic yield, minimizes patient visits, avoids radiation exposure, and provides cost-effective comprehensive evaluation in the office setting 1.