Using corpus luteum formation with dominant follicle collapse to improve the criteria for identifying ovulation

Thomas P Bouchard; Roger Pierson; Rene Ecochard; Michael Lane; Grace E Alger; Chloe J Diment; Mohamed Bedaiwy; Paul J Yong; Patricia K Doyle-Baker

doi:10.1016/j.rbmo.2026.105660

Diagnostics · Ultrasound

Using corpus luteum formation with dominant follicle collapse to improve the criteria for identifying ovulation

Bouchard TP, Pierson R, Ecochard R, Lane M, Alger GE, Diment CJ, Bedaiwy M, Yong PJ, Doyle-Baker PK

Published July 2026 Reproductive biomedicine online

DOI 10.1016/j.rbmo.2026.105660 PMID 42105719

RRM Academy Synopsis

Trained sonographers date ovulation on ultrasound with high agreement

Trained sonographers agreed closely on the day of ovulation when they used follicle collapse and corpus luteum criteria. A Canadian clinic followed 40 women with regular cycles through 85 cycles, with a median of six scans per cycle. The corpus luteum settled the ovulation day in 14 of 71 analyzed cycles.

Key Findings

Forty women contributed 85 cycles and 503 ultrasound scans, a median of six scans per cycle.
Of the 85 cycles, 2 had too little data, 1 showed an incidental dermoid cyst, and 11 showed patterns without ovulation, leaving 71 cycles for analysis.
Identifying the dominant follicle and its collapse settled the ovulation day in 57 of 71 cycles (80%). Corpus luteum assessment settled it in the other 14 cycles (20%).
In this cohort of 71 cycles, inter-rater reliability between two sonographers was high (P < 0.0001). Of the experienced sonographer's dates, 91% fell within 1 day of the review panel's date.
After excluding the 3 cycles with too little data or a dermoid cyst, 11 of 82 cycles showed no ovulation, an 87% ovulation rate.

Interpretation

The study is a single-clinic reliability study in 40 women aged 18 to 45 with regular cycles. Women with conditions that impair ovulation or fertility, such as endometriosis, were excluded, so the study did not include them. Agreement between raters measures consistency. Hormone data were collected and are left for a later step. One ultrasound machine was used, and some scans were missed. Five women withdrew after the first scan because of nervousness or discomfort. The scans were part of a urine fertility monitor study, and the lead author's PhD is co-funded by the monitor's developer.

RRM Context

Fertility awareness methods use signs such as cervical mucus and basal body temperature. The paper states that these signs need checking against an ultrasound day of ovulation. A fixed ultrasound definition gives that check a common reference. The authors say studies should also report cycles with no ovulation, including follicles that form but release no egg.

Our editorial summary of this paper, not the article's abstract.

Abstract

Research Question

Does formation of the corpus luteum help to identify the day of ovulation on ultrasound when follicular collapse is missed, and how reliable are sonographers versus a review panel in identifying the day of ovulation on ultrasound?

Design

Sonographers in a clinic in Canada performed serial endovaginal ultrasound scans (six to eight per cycle) to identify the day of ovulation in regularly cycling women (n = 40) who were followed for one to five cycles (n = 85). The day of ovulation was identified by: (i) identification of the dominant follicle; (ii) disappearance of the dominant follicle; and (iii) identification and dating of the corpus luteum. The main outcome measures were inter-rater reliability between two sonographers, and Bland-Altman agreement between the supervising sonographer and a panel that reviewed each scan to identify the day of ovulation.

Results

Of the 85 menstrual cycles reviewed, two cycles did not have sufficient data to date ovulation, one cycle showed an incidental dermoid cyst, and 11 cycles showed anovulatory patterns. This left a total of 71 cycles (84%) for which intra-rater reliability between two sonographers for identifying the day of ovulation was high (intraclass correlation coefficient = 0.99, P < 0.0001), and Bland-Altman agreement showed no significant difference in the estimated day of ovulation between the supervising sonographer and the panel (t = -0.28, P = 0.78). Corpus luteum criteria were necessary to help identify the day of ovulation in 14 of 71 cycles (20%).

Conclusions

The estimated day of ovulation can be determined reliably on ultrasound by trained sonographers using collapse of the dominant follicle and formation of the corpus luteum based on six to eight scans per cycle.

Topics

Diagnostics › Ultrasound › Follicular Monitoring · Menstrual Cycle › Cycle Biomarkers › Hormonal Markers · Research Methods › Measurement and Statistics › Outcome Definitions

Thomas P Bouchard, Roger Pierson, Rene Ecochard, Michael Lane, Grace E Alger, Chloe J Diment, Mohamed Bedaiwy, Paul J Yong, Patricia K Doyle-Baker

Tom Bouchard, T Bouchard, R Pierson, R Ecochard, Mike Lane, M Lane, G Alger, C Diment, M Bedaiwy, P Yong, Pat Doyle-Baker, Trish Doyle-Baker, P Doyle-Baker

PMID 42105719 42105719 DOI 10.1016/j.rbmo.2026.105660 10.1016/j.rbmo.2026.105660 Bouchard et al. 2026, Bouchard 2026

Using corpus luteum formation with dominant follicle collapse to improve the criteria for identifying ovulation

Trained sonographers date ovulation on ultrasound with high agreement

Key Findings

Interpretation

RRM Context

Abstract

Topics

By this author

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