A LONGITUDINAL-STUDY DESCRIBING CONFIDENCE-LIMITS OF NORMAL FETAL CARDIAC, THORACIC, AND PULMONARY DIMENSIONS FROM 20 TO 40 WEEKS GESTATION

The current prospective, longitudinal study was designed to define the confidence limits and characteristics of growth for fetal cardiac, th oracic, and pulmonary dimensions from 20 to 40 weeks' gestation. We te sted the hypotheses that (1) CC/TC, (2) CC/AC, (3) TC/HC, and (4) TC/A C ratios remain constant throughout this period of gestation. The four -chamber view of the fetal heart in diastole, in the absence of fetal breathing, was used as a standard reference for sonographic measuremen t of cardiac, thoracic, and left and right pulmonary dimensions in a l ongitudinal study of 45 uncomplicated pregnancies. Cardiac growth is b est fit by a quadratic function: -8.147 + 0.900 (GA) -0.0078 (GA)(2). Similarly, thoracic growth is best fit by a quadratic function: -14.07 2 + 1.757 (GA) -0.018 (GA)(2). The characteristics of growth of the le ft and right lungs are best described by linear growth equations: -1.7 1 + 0.426 (GA) and -1.62 + 0.539 (GA), respectively. Each of the CC/TC , CC/AC, TC/HC, and TC/AC ratios changed significantly over time. KEY WORDS: Fetal cardiac dimensions; Fetal thoracic dimensions; Fetal pulm onary dimensions.