Pregnant mare serum is a biological product derived from pregnant mare urine that contains high levels of estrogen. However, some people may prefer to use alternative names for this product to avoid using animal-derived products or to provide more clarity. Some synonyms for pregnant mare serum include conjugated equine estrogens, equine estrogens, and conjugated estrogenic hormones. Additionally, some individuals may use the brand name of the specific product they are using, such as Premarin or Enjuvia. It is important to always check with a healthcare provider or veterinary professional to ensure that the correct product and dosing is being used for a specific medical condition or use in veterinary medicine.