A follicular volume of >0.56 cm3 at trigger is the cutoff to predict oocyte maturity: a starting point for novel volume-based triggering criteria.

ABSTRACT

OBJECTIVE: To determine the minimum follicular volume on the day of trigger that will correspond to a mature oocyte at egg retrieval by individualized follicular puncture and to calculate the mean follicular growth from ovulation induction to egg retrieval using SonoAVCfollicle. DESIGN: A prospective observational study of 53 women undergoing in vitro fertilization, in which it was possible to identify unequivocally one or more follicles at trigger and egg retrieval using three-dimensional ultrasound. SETTING: University-affiliated private in vitro fertilization center. PATIENTS The final sample included 206 follicles from 14 oocyte donors and 39 patients. INTERVENTIONS: A three-dimensional ultrasound with SonoAVCfollicle was performed at trigger and egg retrieval. The same operator selected follicles that were identified easily on both scans and verified that they were apt to be aspirated individually. Follicles were punctured individually, recording the real aspirated volume and the maturity stage of the oocyte. MAIN OUTCOME MEASURES: The primary outcome was the relationship between follicular volume on the day of the trigger and the oocyte maturity stage. The secondary outcome was the rate of follicular growth from the day of trigger to the day of oocyte retrieval, as measured using SonoAVCfollicle. RESULTS: On the day of trigger 206, follicles were selected. Of these, 5 could not be identified on the day of oocyte retrieval, probably because of follicular rupture (mean volume 4 cm3, range 2-7 cm3), and in 48, an oocyte was not obtained. The relationship between follicular volume and oocyte maturity was studied in 153 follicles 125 (82%) contained mature and 28 (18%) contained immature oocytes. Receiver operating characteristic curves showed an area under the curve value of 0.73 (95% confidence interval 0.65-0.80). A follicular volume of >0.56 cm3 is the cutoff point, with the highest Youden index having a sensitivity of 85% and a specificity of 64% to predict oocyte maturity. The mean follicular growth from trigger to egg retrieval was 26%-50% in 53% of cases. CONCLUSION: A follicular volume of >0.56 cm3 at trigger is the cutoff point with the optimal balance between sensitivity and specificity for oocyte maturity. Follicles of >2-3 cm3 may undergo spontaneous rupture before egg retrieval. Given these findings, we propose new volume-based criteria for trigger 70% of follicles of >0.6 cm3 and dominant follicles between 2 and 3 cm3. These findings need validation by randomized controlled trials.