Postpartum Preeclampsia: This condition is characterized by the onset of hypertension and often proteinuria after 20 weeks of gestation, but it can also present postpartum. The symptoms of headache and elevated blood pressure one week postpartum are consistent with postpartum preeclampsia, which can occur up to 6 weeks after delivery.

Postpartum Hypertension: This is a condition where blood pressure elevates postpartum without the proteinuria typically seen in preeclampsia. It can cause headaches and is a common issue in the postpartum period.
Migraine: Migraines can be exacerbated by hormonal changes postpartum and can present with headache and sometimes elevated blood pressure due to pain.
Tension Headache: Stress and sleep deprivation common in the postpartum period can lead to tension headaches, which might be accompanied by mild blood pressure elevations.

Postpartum Hemorrhage (PPH) with Hypovolemic Shock: Although less directly related to headache and hypertension, PPH can lead to a cascade of events including hypovolemia, which might cause headache and could initially present with hypertension due to stress response before progressing to hypotension.
Pituitary Apoplexy: A rare but potentially life-threatening condition where a pituitary tumor undergoes hemorrhage or infarction, leading to sudden headache, visual disturbances, and potentially altered mental status. It's crucial to consider in the differential due to its severity.
Subarachnoid Hemorrhage: A severe condition that can present with sudden, severe headache (often described as "the worst headache of my life") and elevated blood pressure. It requires immediate medical attention.

Reversible Cerebral Vasoconstriction Syndrome (RCVS): A rare condition characterized by temporary narrowing of the blood vessels in the brain, often presenting with sudden, severe headaches and sometimes elevated blood pressure. It can be triggered by postpartum hormonal changes.
Postpartum Thyroiditis: An inflammatory condition of the thyroid gland that can occur postpartum, leading to transient hyperthyroidism, which might cause headaches and elevated blood pressure among other symptoms.
Cerebral Venous Thrombosis: A rare condition where a blood clot forms in the brain's venous sinuses, which can present with headache and elevated blood pressure, among other neurological symptoms. It's more common in the postpartum period due to hypercoagulability.