CFS: Chr. Fatigue S. Chronic fatigue syndrome is poorly understood. Many things have been blamed to cause it i.e. Epstein barr virus, cyromegalovirus, toxoplasmosis. Most of the time we don't find a cause. During pregnancy many hormones are produced by the placenta and there is some biochemical interaction between fetus and mother. In general pregnancy causes fatigue especially at the end. Pregnancy triggers cfs?