Cerebral Venous Thrombosis (CVT): Given the patient's history of miscarriage, which is a hypercoagulable state, and the presentation of headache, confusion, altered mental status, and focal neurological deficits (weakness of right leg and left arm), CVT is a strong consideration. The condition can lead to increased intracranial pressure and ischemic damage, explaining the symptoms.

Ischemic Stroke: The patient's symptoms of weakness in one leg and the opposite arm could indicate a stroke, possibly due to a cardioembolic source or atherosclerosis. However, the presence of headache and altered mental status might suggest a more complex or severe stroke.
Hemorrhagic Stroke: Although less likely than ischemic stroke, hemorrhagic stroke could present with sudden headache, confusion, and focal neurological deficits. The history of miscarriage does not directly increase the risk of hemorrhage but does not rule it out either.
Postpartum Vasculopathy: Although less common, this condition can occur after a miscarriage and presents with headache and stroke-like symptoms due to vasculopathy.

Subarachnoid Hemorrhage: A life-threatening condition that requires immediate diagnosis and treatment. The sudden onset of a severe headache (often described as "the worst headache of my life") and altered mental status could be indicative of a subarachnoid hemorrhage.
Meningitis/Encephalitis: Infections of the meninges or brain tissue can present with headache, confusion, and altered mental status. These conditions are medical emergencies requiring prompt diagnosis and treatment.
Pituitary Apoplexy: Although rare, this condition can occur postpartum and presents with sudden headache, visual disturbances, and altered mental status due to hemorrhage or infarction of the pituitary gland.

Reversible Cerebral Vasoconstriction Syndrome (RCVS): A rare condition that can present with thunderclap headache and sometimes focal neurological deficits. It is often associated with vasoconstriction of cerebral arteries and can occur postpartum.
Cerebral Vasculitis: Inflammation of the blood vessels in the brain can lead to a variety of symptoms including headache, confusion, and stroke-like symptoms. It is a rare condition that might be considered if other diagnoses are ruled out.
Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS): A rare genetic disorder that can cause stroke-like episodes, often with a headache and altered mental status. It would be an unusual diagnosis in this context but could be considered with appropriate clinical and genetic findings.