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Omeprazole comes under category C by the FDA. Its use during pregnancy and lactation is justified only if benefits outweigh the risks. There are however no reported abnormalities seen in the infants born to mothers who were prescribed this drug during pregnancy. Sometimes it is also used to control severe pregnancy induced vomiting (hyperemesis). In recent studies done, no association was found between use of this drug during organogenesis and increased incidence of malformations, spontaneous abortions, decreased birth weight, or perinatal complications. For further discussion and details consider visiting your doctor/gynecologist.
Take care.