Evaluation of The Relationship Between Fetal Lung to Head Ratio and Amniotic Fluid Index in The Third Trimester of Pregnancy

This study assessed the relationship between the ratio of fetal lung volume to head circumference and amniotic fluid index (AFI) in the third trimester of pregnancy.

This prospective study was performed on low-risk pregnant women in their third trimester of pregnancy. Fetal lung volume was determined separately using the lung-to-head ratio (LHR) for the right and left lungs. Moreover, the AFI was evaluated, and the Pearson correlation coefficient between LHR for both lungs and AFI was investigated.

Overall, 112 pregnant women were included in the study. The mean ± standard deviation (SD) of fetal Observed/Expected Right LHR (O/E RLHR) and O/E Left LHR (O/E LLHR) were 113.9±0.36 and 97.13±27.87, respectively. The mean ± SD of AFI was 12.5±4.96 cm. Pearson correlation coefficient did not show a significant relationship between AFI and the left and right LHR (P>0.05). However, O/E RLHR was significantly correlated with abdominal circumference (P=0.02, r=0.2), gestational age (P=0.21, r=0.27), and fetal weight (P<0.001, r=0.27). There was a positive correlation between the number of days the infant was admitted to the neonatal intensive care unit and the volume of the right lung of the fetus (P=0.03, r=-0.2). No correlation was observed between fetal parameters and the volume of the left lung of the fetus.

The results of this study showed that AFI in the third trimester of pregnancy was not significantly correlated with LHR.