hi welcome to healthcare magic.L-arginine is an amino acid.it is necessary for the body to make proteins.it is also found in red meat,paultry,fish,daily products.L-arginine is converted in the body into a chemical called nitric oxide. Nitric oxide causes blood vessels to open wider for improved blood flow. L-arginine also stimulates the release of growth hormone, insulin, and other substances in the body.it is possibly safe when used appropriately short term in pregnancy.not enough is known about using it for long term in pregnancy and during breast feeding.if it supplement along with antioxidant vitamins it can reduce the incident of preeclampsia. It may be a good idea to avoid L-arginine supplements if you are pregnant or thinking about becoming pregnant, unless your healthcare provider recommends that you take L-arginine for a specific medical reason. Pregnancy is not a time to be experimenting with supplements or medications. It is best to stick with products that are known to be safe for pregnant women. Avoid in pregnant or breastfeeding women, due to a lack of sufficient available safety and efficacy data. thanks bye