A 28-year-old female seeks evaluation alongside her partner due to primary infertility. Th… — USMLE Step 2 CK

A $28$ -year-old female seeks evaluation alongside her partner due to primary infertility. The couple has been engaging in regular, unprotected vaginal intercourse for $14$ months without achieving conception. Her menarche occurred at age $12$ . Her menstrual cycles are highly regular, occurring every $28$ days with $5$ days of moderate bleeding. She utilizes a home basal body temperature tracking method, which consistently demonstrates a biphasic monthly pattern. Five years ago, she was treated for a sexually transmitted pelvic infection with a single dose of intramuscular ceftriaxone and a $14$ -day course of oral doxycycline. She takes a daily prenatal vitamin. Her body mass index is $23 \text{ kg/m}^2$ . Vital signs are within normal limits. Physical examination reveals normal female hair distribution, absent galactorrhea, and no cutaneous manifestations of hyperandrogenism. Pelvic examination is unremarkable, with no cervical motion tenderness or adnexal masses.

Recent laboratory studies reveal:
Thyroid-stimulating hormone: $1.8 \mu\text{U/mL}$
Prolactin: $12 \text{ ng/mL}$
Day $21$ serum progesterone: $14 \text{ ng/mL}$

Her partner's semen analysis shows a volume of $3.2 \text{ mL}$ , a sperm concentration of $55 \times 10^6/\text{mL}$ , $65\%$ progressive motility, and $8\%$ normal morphology.

Based on the provided clinical data, what is the most appropriate next diagnostic step for this couple?

A
Measurement of serum total testosterone and dehydroepiandrosterone sulfate
B
Measurement of serum free thyroxine
C
Empiric administration of oral doxycycline and intramuscular ceftriaxone
D
Prescription of clomiphene citrate for ovulation induction
Fluoroscopic examination of the uterus and fallopian tubesAnswer

Answer

The most appropriate next step is a fluoroscopic examination of the uterus and fallopian tubes (hysterosalpingography).

The correct answer involves performing a hysterosalpingography. The initial diagnostic approach to infertility involves evaluating three primary axes: male factors, ovulatory function, and tubal/uterine anatomy. In this scenario, the partner's semen analysis is normal, eliminating a major male factor. The patient's regular menses, biphasic basal body temperature, and day 21 progesterone level of 14 ng/mL (values >3 ng/mL confirm ovulation) demonstrate normal ovulatory function. Given her history of a pelvic infection (PID), she is at high risk for tubal factor infertility due to post-inflammatory scarring and tubal occlusion. Therefore, structural evaluation of the fallopian tubes via hysterosalpingography is the most critical next step.

Step-by-Step Solution

Analyze the male partner's contribution to the couple's infertility.

The semen analysis demonstrates normal volume, concentration, progressive motility, and morphology.

Semen analysis is a primary component of infertility workup; normal results rule out severe male factor infertility.

Assess the patient's ovulatory status based on history and laboratory findings.

The patient has regular menstrual cycles, a biphasic basal body temperature, and a day 21 progesterone level >3 ng/mL.

These findings definitively confirm that the patient is experiencing normal, regular ovulation, ruling out anovulatory disorders such as PCOS or functional hypothalamic amenorrhea.

Evaluate the patient's anatomical risk factors to determine the next diagnostic step.

The patient has a known history of a sexually transmitted pelvic infection (PID).

PID is a major risk factor for fallopian tube scarring and obstruction. Because male and ovulatory factors are normal, the structural integrity of the reproductive tract must be assessed via hysterosalpingography.

Key Concept

The initial evaluation of primary infertility requires a systematic assessment of male factors (semen analysis), ovulatory factors (menstrual history, mid-luteal progesterone), and anatomical factors (tubal patency via hysterosalpingography), particularly when historical risk factors for tubal disease are present.

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