As with any drug or substance you are considering using while pregnant or nursing, avoid cannabis until after your pregnancy has ended. If you have a pre-existing medical condition, including heart disease and high blood pressure (high blood pressure), avoid using cannabis as it can make your symptoms worse. If your family has a history of paradoxical mental syndrome and/or other forms of cyclic vomiting syndrome (CVS), also known as related conditions such as hyperemesis gravidarum (HG) during pregnancy – a severe form of morning sickness in which women vomit continuously throughout their pregnancy Avoid marijuana use completely.