Division of Clinical Research, Climax Radiology Education Foundation, Tehran, Iran; Division of Clinical Research, Iranian Association of Fetal Ultrasound, Tehran, Iran
Fetal lung immaturity is considered as an important
factor for adverse neonatal complications such as respiratory distress syndrome. Therefore, multiple attempts have been made to determine prenatal lung maturity. Currently, the gold standard for this purpose is amniocentesis in order to examining lecithin to sphingomyelin ratio of the amniotic fluid. However, amniocentesis is an invasive testing that can cause maternal and/or fetal complications. Fetal pulmonary artery Doppler study is a non-invasive method that may be helpful in predicting fetal lung maturity and preventing postnatal complications.
To investigate the efficacy of fetal pulmonary artery Doppler examination as a predictor of fetal lung maturity.
Patients and Methods:
86 singleton pregnancies with indication of emergent cesarean section before 37 weeks of gestation were included in a prospective study. Pulmonary artery Doppler exam was performed and interpreted by an expert radiologist, 1-12 hour(s) prior to delivery. Fetal main pulmonary artery resistive index (RI), pulsatility index (PI), and acceleration time to ejection time (AT/ET) were determined using manual tracing of three contiguous waves (for RI and PI) and manual determination of times on one wave (for AT/ ET). None of included mothers had comorbidities and/or received corticosteroids after Doppler examination. NICU admission and/or neonatal death due to respiratory distress were considered as adverse postnatal outcome.
Gestational age at delivery was between 31 and 37 weeks. 16 neonates (19%) required NICU admission because of respiratory distress. No neonatal death occurred during 1-month follow-up. Gestational age was lower in NICU-admitted newborns compared to non-NICU-admitted ones (mean, 33.8±1.3 weeks versus 35.4±1.9 weeks, P =0.002). Pulmonary artery RI (mean, 0.86±0.15 versus 0.81±0.24, P =0.52)
as well as PI (mean, 2.18±0.27 versus 2.25±0.41, P =0.43) was not statistically different between NICU-admitted and non-NICU-admitted neonates. However, pulmonary artery AT/ET was found to be significantly lower in newborns with respiratory distress in comparison to those without respiratory distress (mean, 0.24±0.05 versus 0.33±0.09, P
<0.001). Receiver operating characteristic curve demonstrated that the optimal cut-off point for predicting fetal lung maturity based on pulmonary artery AT/ET is 0.31 with the ratios ≥0.31 indicating fetal lung maturity (sensitivity =75%, Specificity
=93%, negative predictive value =85%, positive
predictive value =82%).
In conclusion, fetal pulmonary artery acceleration time to ejection time is a useful Doppler parameter for predicting fetal lung maturity non-invasively.