Prediction of abortion interval and misoprostol dose using strain elastography in mid-trimester abortions. Cross sectional study

Demographic and clinical data, including age, gravida, parity, weight (kg) and height (cm), were collected through a questionnaire. Body mass index (BMI) was calculated (kg/m2). Patients’ groups related with previous delivery types were recorded as; prior cesarean delivery (without any vaginal delivery), nulliparous and vaginal delivery (with or without cesarean).

Fetal termination causes were grouped as; fetal anomaly, fetal death, rupture of membranes (RM). Following US and elastographic measurements, misoprostol protocol was initiated. Following the administration of both sublingual and vaginal 200 µg misoprostol, a 200 µg sublingual misoprostol was continued every 3 hours until abortion process was completed.

Our clinic is a tertiary referral center, and due to the high number of complicated obstetric patients, a relatively low-dose misoprostol protocol was applied to avoid increasing complications. A total of 67 patients were included the study. No patient was included in more than one group that was described previously.

When the termination process was completed; total misoprostol doses, abortus time intervals (minute), fetal weight (gram) data were recorded.Elastography method:SE technique was defined and figures were added to ensure reproducibility. The strain measurements are displayed on a semi-transparent colored map called an elastogram, which is overlaid on the B-mode image (Fig. 1). Typically, low strain (stiff tissue) is displayed in blue, and high strain (soft tissue) is shown in red, although the color scale can vary, depending on the US vendor.

SR, a pseudo-quantitative measurement, compares stiffness of different tissues as a target and a reference tissue. SR >1 shows the target lesion compresses less than the reference tissue, indicating lower strain and greater stiffness (Choi et al. 2015). With this information, 1 hour before the intervention each patient’s cervix and uterus were examined in the midsagittal plane using the transvaginal B-mode US.

Cervical length (CL) was measured internal cervical os to external cervical os in midsagittal plane. Fetal biometry was recorded as biparietal diameter (BPD), abdominal circumference (AC), femur length (FL) and estimated fetal weight (EFW). With the elastography mode of US, the reference (anterior lip of external cervical os) and target (anterior lip of internal cervical os) region of interest (ROI) were determined, and compression and decompression cycles were applied with the transvaginal probe manually.

SR was calculated at the peak of the pressure in the area where the trace was regular. SRs were calculated at least three times, and the mean SR was saved. All US examinations were performed by a single gynecologist with Voluson S8 (GE Healthcare, Chicago, IL, USA, equipped with a 4.0–9.0 MHz multifrequency transvaginal probe).