ABSTRACT
Objective: To quantitatively analyze the fetal lung echo and right lung volume in the third trimester by real-time three-dimensional ultrasound (3-D US) and evaluate the feasibility of fetal lung maturity. Methods: A total of 732 women with normal singleton pregnancies between 28 and 42 weeks of gestation underwent ultrasound examination. The 3-D US equipment with a 3.5-5 MHz transabdominal transducer was used for the fetal biometric measurement. The echogenicity ratio between fetal lung and liver was compared. The fetal lung volume was calculated by the rotational multiplanar technique for volume measurement (VOCAL). Results: The right fetal lung volume increased with the increase of gestational age with a linear positive correlation (r = 0.884, P<0.01). After 34 weeks, the echogenicity ratio of fetal lung to liver was more than 1.1. Conclusion: The echogenicity of lung/liver and fetal lung volume could be used as normal fetal predictable indicators for fetal lung maturity.