Headaches during pregnancy are usually due to high hormone levels. Hormonal headaches often diminish later in pregnancy. However, if you have pre-existing headaches, they may worsen during pregnancy.
Pregnancy headaches are rarely dangerous, but it's essential to consider them as an indication that you need to take it easy. Common reasons for headaches, besides hormonal changes, include dehydration, poor sleep, stress, or an impending cold.
If you experience severe headaches combined with increased swelling, it could be a sign of developing preeclampsia. Always contact your midwife for advice and assessment if you are unsure.