An imbalance between oxidative stress and maternal detoxification or antioxidant capacity may explain the symptoms of preeclampsia and the haemolysis-elevated liver enzymes-low platelets (HELLP) syndrome. Oxidative stress is known to induce damage of the endothelium, which is one of the pathophysiological features of preeclampsia and the HELLP syndrome. Administration of N-acetylcysteine, an antioxidant itself and a precursor of the endogenous antioxidant glutathione, might stabilize or even partly recover the process of endothelial damage and may lead to prolongation of pregnancy.