Abstract

The radial count method of Emery and Mithal was applied to the lungs of 37 infants of gestational age 19-42 weeks. The method could be used satisfactorily to evaluate airspace-containing lungs, whether alveolated or non-alveolated (saccule-containing). There was a progressive increase in complexity of terminal lung units throughout gestation, and a smooth transition was effected at 1 month of age between the radial counts of the intrauterine cohort and those of a separate group used to study postnatal lung growth. In the intrauterine and early postnatal group radial count results correlated very closely with the total gestational age (gestational age plus survival time after birth) of the child (r = +0.93). Prior inflation of the lungs affected the radial counts of alveolated lungs much more than those of saccule-containing lungs, so that results correlated most closely with those of Emery and Mithal in the period up to 34 weeks' gestation. Radial count estimation correlated better with total gestational age, crown-rump length, body weight, and fixed lung volume than did any other morphometric parameter assessed. The radial count method provides a reliable index of lung growth in intrauterine and early postnatal development.