Interestingly, the authors found an apparent reduction in the expression of IL-6 in pregnant women with periodontal disease compared to that in pregnant women without periodontal disease, which is in agreement with the previous in vitro study mentioned above that reported that high levels of progesterone during pregnancy had an inhibitory effect on the secretion of IL-6 by human GFs in response to IL-1 [71]. This evidence concerns the gene IL1B and periodontal disorder.