Role of Echogenic Amniotic Fluid Particles and Optical Density in prediction of Respiratory Distress Syndrome and Labor

Abstract

This study was aimed to correlate echogenic amniotic fluid particle size (AFPS) in late third trimester to fetal lung maturity and amniotic fluid optical density (AFOD) at labor. AFPS were measured with specified criteria by real time transabdominal USG (3.5MHz) while Amniotic Fluid Index (AFI) was measured during routine antenatal visits. The criteria for AFPS score which are taken into account are the amniotic fluid particle size, number and distribution. Serial AFPS measurements were done till onset of labor. AFPS was correlated to AFOD value at spontaneous labor in 123 women.  Uncentrifuged fresh amniotic fluid samples were obtained during ARM/amniotomy and used for AFOD estimation at 650 nm. The mean AFPS and AFOD at onset of labor was found to be 5.14 ± 0.69 mm (3.67 – 6.7 CI 95%) and 1.03 ± 0.31 (0.35 -1.69 CI 95%) respectively in 116 women who delivered normal babies devoid of respiratory distress syndrome (RDS). Serial AFPS measurements showed a definite AFOD surge after a value in the region of 3.8 mm which is obtained culminating in onset of Labor. 28 women (24.1%) had dense clusters of free floating particles across the vertical pool in amniotic fluid with mean AFPS and AFOD of 5.6 ± 0.68 mm and 1.12 ± 0.21 respectively. In 123 women, AFPS < 3.8 mm had sensitivity of 85.74% and positive predictive value of 66.67% in predicting RDS. AFPS serves as a sonological marker for fetal lung maturity and labor. The range of AFOD values can be measured in terms of AFPS (r =0.6, F = 69.8, β= + 0.23, p < 0.001). Serial AFPS estimation predicts fetal maturity and onset of labor.

KEY WORDS: Amniotic fluid; Particle size; Optical density; Respiratory
distress syndrome; Labor