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

Background & Objective: 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. Materials & Methods: 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. Results: Overall, ۱۱۲ 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 ۱۱۳.۹±۰.۳۶ and ۹۷.۱۳±۲۷.۸۷, respectively. The mean ± SD of AFI was ۱۲.۵±۴.۹۶ cm. Pearson correlation coefficient did not show a significant relationship between AFI and the left and right LHR (P>۰.۰۵). However, O/E RLHR was significantly correlated with abdominal circumference (P=۰.۰۲, r=۰.۲), gestational age (P=۰.۲۱, r=۰.۲۷), and fetal weight (P<۰.۰۰۱, r=۰.۲۷). 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=۰.۰۳, r=-۰.۲). No correlation was observed between fetal parameters and the volume of the left lung of the fetus. Conclusion: The results of this study showed that AFI in the third trimester of pregnancy was not significantly correlated with LHR.

Keywords:

Amniotic fluid index , Lung hypoplasia , Lung to head ratio , Oligohydramnios