Most pregnant women with primary headaches have diagnosis before pregnancy
10% of pregnant women will have new onset headache during gestation
1/3 due to migraine
1/3 due to pre-eclamptic toxemia (PET)/eclampsia
1/3 due to migraine
1/3 due to pre-eclamptic toxemia (PET)/eclampsia
Headache during pregnancy
Consider usual differential for headaches
Cardiac arrest in pregnancy
Also consider preeclampsia/eclampsia 
Abdominal pain in pregnancy
New onset of severe headache in no history of migraines → maintain high suspicion of[1]:
Vaginal bleeding in pregnancy 
ICH