Omeprazole (Omizac) is under FDA Category C, meaning animal studies revealed harmful effects to the fetus but no controlled human studies were done, or both human and animal studies are not available. The use of this medication is only allowed when clearly needed and if the benefits of the drug outweigh the risks.. You should have consulted your wife's OB gyne prior to taking the medication in order to properly diagnose the pain she experienced and give her the right medicine for it. There are other safer antacids pregnant women can use like calcium carbonate or magnesium hydroxide (if the pain she experienced are due to hyperacidity or heartburn, etc). Always consult the OB gyne prior to taking any medications when pregnant.