Food aversions or cravings When you're pregnant, you might find yourself turning up your nose at certain foods, such as coffee or fried foods. Food cravings are common, too. Like most other symptoms of pregnancy, these food preferences can be chalked up to hormonal changes — especially in the first trimester, when hormone changes are the most dramatic. Headaches Early in pregnancy, increased blood circulation caused by hormonal changes may trigger frequent, mild headaches. Constipation Constipation is another common early symptom of pregnancy. An increase in progesterone causes food to pass more slowly through the intestines — which can lead to constipation.