Reference ranges for 2-dimensional sonographic lung measurements in healthy fetuses: a longitudinal study.

OBJECTIVES

The purpose of this study was to establish reference ranges for 2-dimensional sonographic measurements of fetal lungs from longitudinal data.

METHODS

A total of 214 fetal lung measurements were longitudinally evaluated in 62 healthy fetuses between 20 and 36 weeks' menstrual age. Both right and left lung areas were measured in the heart 4-chamber view using lung area tracing and axis diameter methods. Multilevel modeling was used to evaluate the expected values and variability with respect to menstrual age and to generate reference ranges for the lung area, lung-to-head ratio, quantitative lung index, and observed-to-expected lung-to-head ratio for both lungs.

RESULTS

The expected values varied with menstrual age for all parameters. Variance was menstrual age dependent for all parameters except the longest diameter area measurements and their lung-to-head ratios.

CONCLUSIONS

Models are presented for expected 2-dimensional sonographic lung size parameters and their variance as a function of menstrual age. These data have been used to generate age-specific reference ranges for both measurements and indices.