It hasn't been well studied in pregnancy, so the cautious, honest answer is not to start it while pregnant or breastfeeding without a physician's guidance
The consideration of cysteine during these simulations were important, as cytosolic cysteine is the rate limiting amino acid precursor for synthesis of GSH, via the -glutamylcysteine synthetase (GCS) enzyme, and this is a function of its reduced concentration compared to the other precursors, glycine and glutamate
While it can help improve your skins health and appearance, its effectiveness depends on various factors, including your Skin Type , the cause of your Acne , and how you use it
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Further randomized and well-controlled studies are needed to confirm these preliminary findings