Ultrasound Evaluation of Uterine Cavity Changes After Stimulation for In Vitro Fertilization

Mock embryo transfer (ET) before in vitro fertilization (IVF) allows for the clinical determination of uterine cavity length (UCL) to optimize embryo placement during clinical ET. Most studies have shown that optimal pregnancy rates occur with clinical ET at a depth of 15 mm from the uterine fundus. In our study, we sought to determine the effect of ovarian stimulation and endometrial preparation on UCL using 2D transabdominal ultrasound.

We performed a retrospective cohort study comparing documented 2D transabdominal ultrasound measurements of UCL at the time of mock ET and clinical ET. Statistical analyses were performed with SPSS v. 26 with paired sample t-test and significance determined with P < .05.

Seventy patients who underwent 91 IVF-ET cycles between 2015 and 2018 at our academic center met inclusion criteria. Patient's demographics include a median age of 34 (interquartile range [IQR]: 31, 37), gravida 1 (IQR: 0, 2), parity 0 (IQR: 0, 0), and body mass index 25.87 (IQR: 21.78, 30.01). There was a statistically significant increase in UCL by 11.9 mm after IVF stimulation (P < .001), compared to mock ET. Mean UCL at the time of mock ET was 7.66 cm (±0.98 cm) and at clinical ET was 8.85 cm (±0.98 cm).

The uterine cavity undergoes a significant length change during ovarian stimulation and endometrial preparation. These findings confirm the remarkable uterine plasticity in response to hormonal stimulation even before pregnancy ensues. These changes in UCL should be considered during ultrasound-guided clinical ET to ensure optimal embryo placement.