It is generally advised to avoid consuming energy drinks like Celsius or Red Bull if you are pregnant or breastfeeding. These drinks contain high amounts of caffeine and other stimulants, which can cross the placenta and affect the developing fetus or pass into breast milk. Caffeine consumption during pregnancy has been associated with an increased risk of miscarriage and low birth weight. It's best to consult with your healthcare provider for personalized advice regarding caffeine intake during pregnancy or breastfeeding.