Preliminary report on a new and noninvasive method for the assessment of fetal lung maturity

Several patterns of fetal breathing movements (FBMs), i.e. abdominal wall movements (AWm), thoracic wall movements (TWm) and nasal fluid flow velocity waveforms (NFFVW), were investigated by ultrasound (US) technology and related to fetal pulmonary maturity and immaturity, i.e. fetal lung maturity (FLM) tests, in order to validate the hypothesis that they may indicate whether the fetal lung is mature or immature, regardless of gender, weight and gestational age.

We prospectively enrolled 143 high-risk pregnancies in which a complete US study of FBMs and FLM tests was performed. Among them 43 women satisfied the inclusion criteria. US-FLM was defined as the presence of regular NFFVW detected by pulsed Doppler and spectral analysis, or irregular NF-FVW synchronous with TWm detected by M-mode. An US guided amniocentesis was performed in order to collect amniotic fluid (AF) and FLM was evaluated by L/S (lecithin/sphingomyelin) determination, presence of phosphatidylglycerol (PG) and lamellar bodies (LBs) count. At the end of the study the diagnostic accuracy of US-FLM was compared to that of FLM tests.

Diagnostic accuracy for US evaluation of FLM was as follows: sensitivity: 89.6%; specificity: 85.7%; PPV: 92.8%; NPV: 80%. Diagnostic accuracy of FLM tests was as follows: sensitivity: 100%; specificity: 51.7%; PPV: 100%; NPV: 50%. L/S determination predicted lung maturity with a sensitivity of 100%; specificity of 93.1%; PPV of 100%; NPV of 87.5%.

Presence of regular NFFVW or irregular NFFVW and TWm correlate accurately with conventional FLM tests. We suggest that this noninvasive procedure may be helpful for assessing FLM, particularly under certain circumstances, e.g., oligo-anhydramnios, laboratory logistic equipment difficulties or heavily stained AF samples, amniocentesis refusal, religious concerns.