If you're like most people, you tackle a headache with an over-the-counter pain reliever. Then you charge on with your busy life. If you're pregnant, though, the type of medication you can take is seriously restricted. It's a cruel irony, since some of the common hallmarks of pregnancy -- such as fatigue, low blood sugar, and hormonal mood swings -- can also trigger headaches.
In general, most headaches are considered tension headaches, and they're usually described as a tight band of pain around the head and sometimes at the back of the neck. Emotional factors (like stress) often cause them, but there's a wide range of physical causes too. Eyestrain (from poor lighting or sitting too long at a computer), for example, can bring on a headache. Sinus headaches (pain behind the forehead, cheeks, or the bridge of your nose) are less common, but they happen if an infection or allergy causes an inflammation that blocks mucus from draining into the nose.
Finally, there are migraine headaches. If you've endured them, you know that the word "headache" doesn't quite describe the debilitating pain, which is often associated with nausea or sensitivity to light or noise. A wide range of things can trigger migraines, including weather changes, menstrual cycles, and certain foods.