IL6 and Global developmental delay: The Early markers for Autism study found that high levels of IL-4, IL-5 and interferon-γ (IFN-γ) in maternal serum at 15–19 weeks of gestation were associated with a 50% higher risk of ASD, whereas high levels of IL-2, IL-4 and IL-6 was associated with developmental delay in the absence of ASD (163).