Kermanshah University of Medical Sciences
Predicting the exact time of ovulation is highly important for planning to conceive or prevent pregnancy. This study aims at assessing the accuracy of doppler ultrasound in determining the ovulation time.
The present descriptive cross-sectional study was conducted on 158 women, who intended to conceive. All participants underwent transvaginal doppler sonography of the ovaries between 9th-14th day of menstrual cycle, using A 7-10 Mhz transducer while tissue harmonic imaging function was on. Antral follicles were spotted and their morphological features along with doppler indices in vessels surrounding follicular wall were evaluated (namely peak systolic velocity (PSV), pulsatility index (PI), and resistive index (RI)). Pulse repetition frequency (PRF), and color gain were set as respectively highest and lowest values which give an artifact-free color image.
Approaching toward the 14th day of menstural cycle follicle became larger, more round in shape with a slight increase in their internal echo and occasionally appearance of a surrounding hypoechoic halo. Overtime, perifollicular vessels attained a more uniform configuration and all doppler indices showed significant alteration from ninth to fourteenth day as follow: PSV increased from 18.25±5.811 cm/second on 9th day to 22.37±6.880 on 14th day, PI slightly increased from 2.35±1.327 in 9th day to 2.40±1.347 in 14th day, and RI decreased roughly to the half (from 1.51±6.199 in 9th day to 0.83±0.207 in 14th day). All changes were statistically significant (P<0.05).
With ovulation time approaching, antral follicle shows morphological and vascular changes in ultrasound exam. From 9th To 14th day of menstural cycle, follicular RI decreases, PI gently increases, and PSV increases. These findings reflect higher blood flow velocity and lower vascular resistance around ovulating antral follicle, which is readily identifiable in doppler study and is of great accuracy in estimating the due time of ovulation.