Hi Dear , As per your query you are 28 week pregnant and you are facing difficulty in quitting marijuana . well when you smoke marijuana, you can feel profound and immediate effects. But once those effects are gone, marijuana metabolites remain. This means that chemical remnants of the plant are still present within your body. Usually when person undergo tests it detects metabolites like cannabinoid tetrahydrocannabinol (THC) . Marijuana can stay for months in your body depending upon many factors like basal metabolic rate , body structure , amount and frequency of taking it , I would suggest you few methods to remove it as quickly as possible :- - Wheatgrass Juice , the chlorophyll in wheatgrass is what makes it so cleansing as cholorophyll is a potent blood, liver and gastrointestinal cleanser. - Lacto-Fermented Foods and Beverages . - Regular soaking baths with epsom salts or magnesium flakes will help to open the elimination channels both via the skin and the gut to rid the body of unwanted toxins. Hope your concern has been resolved. Get Well Soon. Best Wishes, Dr. Harry Maheshwari