Comparison of three types of ultrasound transducers in evaluating the amniotic fluid index

The purpose of this study was to determine whether there was good correlation between amniotic fluid index measurements obtained with different types of ultrasound transducer. Women undergoing obstetric ultrasonography for multiple indications between 26 and 40 weeks' gestation had the four-quadrant amniotic fluid index measured with three ultrasound transducers: 3.5-MHz linear, 3.5-MHz sector and 3.5-MHz convex. Pearson product-moment correlation and linear regression analysis were utilized to compare the amniotic fluid index values. Sixty-five women participated in the study. A statistically significant correlation was noted between the three ultrasound transducers evaluated (P < .001). Placental location did not appear to affect the results. Amniotic fluid index values obtained with the sector or convex transducers were as reliable as those obtained with the "gold standard" linear transducer and may be interpreted in the same manner.