Headaches are common during pregnancy (thank you raging hormones), and chances are you if you are pregnant you will begin to see an increase in them around the ninth week.
You could, of course, be one of the lucky few and actually experience a decrease in headaches! In the early stages of pregnancy, headaches can also be caused by an increase in the amount of blood flow, caffeine withdraws, feeling stressed or poor posture.
Like the swelling, however, if you begin to see a sudden increase in the pain, frequency or severity of a headache it could signal a serious pregnancy condition.
If you have a headache that will not go away despite treatment and/or is accompanied by a sudden onset of swelling you should make an appointment with your doctor, this can be another symptom of Pre-Eclampsia.