An ultrasound examination of uterine artery blood flow was performed using a 2.9-MHz (range, 2–5 MHz) transvaginal microconvex probe (GE Voluson E8; GE Healthcare Austria GmbH & Co OG, Zipf, Austria). The examiners were blinded to the history of all subjects.
Ultrasonic Doppler assessment was performed during the midluteal phase at 7 to 10 days after women’s ovulation, which was confirmed by follicular monitoring through an ultrasound examination. Serum progesterone levels were measured during the midluteal phase with an electrochemiluminescence immunoassay (Beckman Coulter, Tokyo, Japan).
Ultrasonic Doppler assessment was performed during the midluteal phase at 7 to 10 days after women’s ovulation, which was confirmed by follicular monitoring through an ultrasound examination. Serum progesterone levels were measured during the midluteal phase with an electrochemiluminescence immunoassay (Beckman Coulter, Tokyo, Japan).