Prospective case control study of 169 women in ART cycles. Infertile couples undergoing ART treatment at our institution were included. Canceled treatments prior to oocyte pickup; cycles with donated gametes; cryopreserved oocyte treatments; cycles for genetic disease screening and embryo selection; cycles with missing or erroneous data; and cycles with elective single embryo transfer were excluded.
The primary data source for this study was the local databases routinely used in the participating centre in ongoing treatments. The data output was anonymized in the extraction for statistical treatment purposes. All data collected and written informed consent was obtained according to the Ethics Committee of our Institution.
Only subjects with viable good grade embryos for transfer (double embryo transfer on day 3 of embryo development) were selected. All subjects have been in a short protocol regimen with antagonist for ovarian controlled stimulation using gonadotropins. All used recombinant human chorionic gonadotropin hormone (rhCG) for induction of ovulation 36 hours prior to oocyte pick up.
Demographics data was collected for all patients and serial ultrasound analysis (endometrial morphology, endometrial thickness, endometrial volume and uterine volume) was performed using the same protocol for all participating subjects.
During ovarian controlled stimulation serial ultrasound exams were performed and serum oestradiol levels obtained for all participants.
Biophysical markers were obtained in all evaluations (Basal moment – day 2 or 3 of women menstrual cycle and prior to begin of ovarian controlled stimulation; at day 6, day 8 and day 10 after initiating ovarian controlled stimulation; at Trigger day with recombinant human gonadochorionic hormone; and at embryo transfer day).
Endometrial morphology was based on the two grade system by Sher et al. (14): non-multilayered homogeneous hyperechogenic or iso-echogenic endometrium compared with the myometrium and multilayered triple-line pattern, ‘halo pattern’ with an outer peripheral layer of denser echogenicity and a central sonolucent area.
Endometrial thinckness was obtained in milimeters (mm) on the long axis or sagittal plane, with the entirely of the endometrial lining through and endocervical canal in view. The measurement was taken of the thickest echogenic area from one basal endometrial interface across the endometrial canal to the other basal surface.
Endometrial volume calculation by 3D ultrasound presented as voxels and geometric information of surfaces in a 3D dataset. The results obtained are then converted to mililitres. Adjusted Endometrial volume was also obtained as a ratio between endometrial volume calculated on 3D analysis and uterine volume based on 3D volumetric acquisitions which then generated an estimated uterine volume (also in mililiters). Adjusted endometrial volume deflects the potential difference in uterine volume from each single individual.
At day 12 after successful embryo transfer, human gonadochorionic sub-unit B serum levels were obtained, and groups were set: positive results (for values over 5 International Units - IU) and negative results (for values under 5 IU).
All data collected was analysed between these two set groups and compared.
Data was analysed in Excel 2019 (Microsoft Corp, Redmond, WA) and IBM SPSS statistics v25 (IBM Corp. Armonk, NY). Continuous variables were analysed with Levene's test (equality of variances) and visual assessment of the histogram (normality).
For analysis of parametric continuous variables, a t-student test for independent samples was used. Chi-square and Fisher’s exact tests were used to analyse associations between categorical variables. Endometrial thickness, endometrial volume and adjusted endometrial volume were analysed using analysis of variance for repeated measurement data.
Value of p < .05 was considered statistically significant.
The authors do not report any conflict of interest.
The study protocol has been approved by the Ethics Committee of our Institution (CHCB 22/2017), in accordance with the relevant guidelines and regulations. This study has been conducted in accordance with legal and regulatory requirements, as well as follow generally accepted research practices described in International Conference Harmonisation (ICH) guidelines, Good Clinical Practices (GCP) and the Declaration of Helsinki.