Headaches in the first trimester of pregnancy may be caused by abnormal hormone levels, lack of sleep, and psychosomatic factors. 1. Abnormal hormone levels: After pregnancy, the hormone levels in the pregnant woman’s body will change significantly, such as estrogen and progesterone, etc., which will cause early pregnancy reactions, manifested as headache, nausea, vomiting, etc. 2. Lack of sleep: many pregnant women in the early stages of pregnancy may have poor sleep quality or insomnia, a long time without reasonable rest, it is easy to induce headaches. 3. Mental and psychological factors: after pregnancy, there may be some mental and psychological abnormalities, such as anxiety or tension, also easy to induce headaches, should adjust the psychological state, reduce psychological pressure, eliminate anxiety, tension and other psychological. Headache in the first trimester of pregnancy, there may be other reasons, when the pain is more serious, you should consult a doctor for examination and treatment to avoid adverse effects.