Lack of eating – Headache during pregnancy is very common it can be due to various reasons the most common cause is not eating on time, acidity is the most common cause. If there is any big gap between meals you can start experiencing headaches. Generally after lunch there will be big gap between lunch and dinner. This can cause headache. Try to take something in between before dinner.
Hormones – Most people experience headaches in first trimester. Try to eat something. If headache still persists have paracetamol which is considered safest medicine during pregnancy.
Stress – During 2nd and 3rd trimesters headaches start coming down. Sleeping helps in keeping your stress levels low. Exercise and not putting too much weight all these things helps to prevent headaches. If headache still persists we cannot always think this due to pregnancy only. This can be neurological cause; in that case you must see a physician.
Sinus – Because of changing weather people have this allergic cold or allergic rhinitis which can lead to headaches.