Nausea and Vomiting
"Morning sickness," or nausea and vomiting that occur in early pregnancy usually happens between weeks two and eight of pregnancy. It's a misnomer because the nausea and vomiting can happen at any time. It's thought changes in levels of estrogen may play a role in developing nausea.
Another early pregnancy sign may be food cravings or aversions. Women may have an unusual urge to eat a particular food, even one she previously did not like, or she may be completely repulsed by a food she used to love. This is common and usually the food aversions fade with the first trimester.