It's not unusual to get tension headaches when you're pregnant, especially in the first trimester. Tension headaches – the most common kind of headache – can feel like a squeezing pain or a steady dull ache on both sides of the head or the back of the neck. If you've always been susceptible to tension headaches, pregnancy can make the problem worse.
Experts don't know exactly why carrying a child tends to make your head ache more often, but one good guess is the hormonal free-for-all that's taking place in your body. Your increased blood volume and circulation may also play a part, especially in early pregnancy. Going cold turkey on caffeine can also make your head pound.
Other potential culprits include lack of sleep or general fatigue, sinus congestion, allergies, eyestrain, stress, depression, hunger, and dehydration.
If you have headaches in your first trimester, you'll probably find that they diminish or even disappear during the second trimester, when the flood of hormones stabilizes and your body grows accustomed to its altered chemistry.
The BabyCenter Medical Advisory Board. (2014). Headaches during pregnancy for Baby Center [Online]. Available: http://www.babycenter.com/0_headaches-during-pregnancy_2035.bc#articlesection1 (May, 2014)