Hello, Ondansetron is a pregnancy category B drug. This means that studies have failed to show any negative effects and thus the drug may be used when deemed really necessary. It is always preferable to use alternate medication and home remedies like honey and lemon to avoid the nausea. Since pregnancy can aggravate the GERD, it is recommended that you eat small quantities at regular intervals. Use of medication to regulate the gut motility is done at the discretion of your consultant. Use a propped up position after eating and do not lie down until one hour after eating to allow easy gastric emptying. Hope this helps.