Morphometric analysis of lung structure with age following in utero gene transfer at 16 days gestation. Amniotic sacs were injected at 16 days gestation with replication deficient adenovirus containing either EGPF, (Control, solid lines), or anti-sense CFTR gene fragment, (Antisense, dashed lines). Morphometric analysis was performed on animals at 2, 4, 7, and 18 months of age. Volume proportions of airways (A), blood vessels (B), and parenchyma (C) are presented as mean ± SEM. *p < 0.05.