Headaches can occur in pregnancy as they can occur at any other time, with the causes being the same as would be the case as if you were not pregnant.
These usual causes can cause headaches to be more prevalent in pregnancy. Common causes include hormonal factors, stress, fatigue, poor sleep, muscle tension, hunger, light headedness, issues with posture, etc. Migraine headaches are usually less in pregnancy but on occasions may be more.
But in pregnancy there is the extra concern cause that the headache may be due to high blood pressure and in particular to a condition such as preeclampsia.
Also if there is a concern about a neurological cause then investigating is more challenging as you are pregnancy.
What can be done about it?
Firstly the cause of the headache needs to be clarified. Do this you will need a medical consultation.
To exclude preeclampsia as the cause you will need a blood pressure check, urine check (for protein) and if concerned a blood test for preeclampsia (checking if present and if so severity). Preeclampsia is confined to more advanced pregnancy, but high blood pressure (without preeclampsia) can be a cause at any stage. With preeclampsia the headache is usually described an extremely severe.
A medical consultation will not only exclude serious causes but also help to tailor management to what is appropriate with consideration of the cause of the headache.
Simple remedies for a non-serious cause headache include rest, lying down (if your headache is due to postural hypotension), adequate fluids, minimising stress, icepack or cold compress on the back of your neck, dark room, massage (especially if headache is due to muscle spasm in the neck), food (if your sugar level is low) and simple analgesia. Analgesic agents such as paracetamol are safe in pregnancy.
Also consider seeing an optometrist to check if yout headache is due to eye strain, adjust your diet, check if your bed is suitable now you are pregnant, maybe cut back on or eliminate coffee, try to avoid places with fluorescent lighting, windowless workspaces, strong odours and loud noises. Watch your posture. Try not to slouching, slumping, or bending over doing close work for long stretches of time. For prevention meditation, relaxation or yoga classes, regular massage or maybe an osteopath, chiropractor or acupuncture can help.
For sinus headaches try Fess nasal spray, steam inhalation and an over the counter nasal decongestant. Make sure you do not have a sinus infection, if so antibiotics will be needed.
If you are a migraine sufferer I will need to check what medications you are taking, as not all are suitable in pregnancy.