Intracycle variation in number of antral follicles stratified by size and in endocrine markers of ovarian reserve in women with normal ovulatory menstrual cycles

Abstract

Objective: To quantify the intracycle variation in markers of ovarian reserve measured by antral follicle counts stratified by size using three-dimensional (3D) ultrasound and anti-Müllerian hormone (AMH) in women with normal menstrual cycles.

Methods: Healthy volunteers with normal menstrual cycles were prospectively recruited. Three-dimensional (3D) ultrasound examination and blood test were performed in early (F1) and mid-follicular (F2) phases and in periovulatory (PO) and luteal (LU) phases of one menstrual cycle. Antral follicles were measured using 'sonography-based automated volume calculation' with post processing (SonoAVC) and ovarian volume was measured using Virtual Organ Computer-aided AnaLysis (VOCAL). Blood serum was processed for hormonal assays including AMH, follicle stimulating hormone (FSH), luteinizing hormone (LH) and estradiol. Repeated-measures analysis was used to examine the variance in markers of ovarian reserve in different phases of one menstrual cycle.

Results: A total of 36 volunteers were included in the final analysis, of whom 34 attended all four visits. Repeated-measures analysis showed a significant variation in total antral follicle count (AFC) (P < 0.001). However, on stratifying the antral follicles according to size using SonoAVC, a non-significant variation (P = 0.382) was seen in small AFC (≤ 6.0 mm) and a significant variation (P < 0.001) was seen in large AFC (> 6.0 mm). The ovarian volume showed a significant intracycle variation (P < 0.001). A small but significant intracycle variation was noted in AMH (P = 0.041) and a significant variation was seen in levels of serum FSH, LH and estradiol (P < 0.05).

Conclusion: Small antral follicles (≤ 6.0 mm) measured using 3D ultrasound and AMH show little intracycle variation and perhaps should be evaluated when predicting ovarian reserve independent of menstrual cycle.