IL17A and major depressive disorder: Depression in pregnancy is also associated with an increase in pro-inflammatory cytokines such as tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), IL-1β and IL-17 [21, 40–45], prompting the question of whether the heightened inflammatory milieu in depression in pregnancy can affect the developing foetus in a similar manner as MIA.