A total of 53 normal fetuses with a gestational age ranging from 15 up
to 39 weeks was investigated and the radial alveolar count (RAC) was
estimated as a parameter for lung maturation. Values lower than 2.0 co
uld only be found in lungs of fetuses aged less than 18 weeks. Between
18 and 25 weeks of gestation, relatively constant levels of RAC were
observed but with considerable interindividual variation. In fetuses w
ith a gestational age of more than 25 and especially 30 weeks, a sligh
t or rapid increase in RAC occurred respectively. Values lower than 3.
0 were found up to a fetal age of less than 30 weeks and a RAC of more
than 4.0 was only found in lungs of fetuses aged more than 30 weeks.
Values exceeding 6.0 occurred only in fetuses at near full-term birth.
Since the estimation of RAC overcomes the effects of varying degrees
of alveolar collapse, such an analysis also seems to be useful for the
determination of fetal age in cases of advanced putrefaction.