Significantly higher densities of c-Fos-ir cells were present in the left HF (1303.7 ± 88 cells/mm2, mean±s.e.m, rounded numbers) compared to the right HF (1151.8 ± 73 cells//mm2) (Fig. 5a) as revealed by a paired sample t-test (t(43) = 2.542, p = 0.015). This evidence concerns the gene FOS and hydrops fetalis.