Preovulatory follicular size: a comparison of ultrasound and laparoscopic measurements.

Ovarian follicles in the immediate preovulatory period were measured with real-time or static ultrasound. Thirty-nine follicles were examined in thirty-six patients. In 29 spontaneous cycles the mean follicular diameter was 21.1 mm (range 17 to 25 mm) and the mean volume was 5.1 ml. In seven stimulated cycles the mean diameter was 18.4 mm and the mean volume was 3.5 ml. Laparoscopic needle aspiration of the follicular contents was performed within 12 hours of ultrasound examination in every case. Follicular dimensions based on the volume of aspirated fluid correlated well with the ultrasound measurements (r = 0.847; P < 0.001), which suggests that ultrasound is a useful technique for examining preovulatory follicular development.