Clinical Reasoning: A 32-Year-Old Woman Presenting With Thunderclap Headache in the Third Trimester.

A 32-year-old gravida 1, para 0 woman at 36 weeks and 6 days of gestation presented to the hospital with a 2-day history of new acute-onset headache. She had no personal or family history of headache, and her medical history was remarkable for colitis treated with vedolizumab. Her pregnancy had been unremarkable, without hypertension or gestational diabetes. MRI with venography and time-of-flight angiography was unremarkable. CSF was negative for signs of inflammation and xanthochromia. She had minimal, transient improvement with nerve block. On the third day of admission, she experienced mild liver enzyme elevation and decreasing platelets. She subsequently underwent cesarian section and delivery of a healthy infant. Her headaches improved and resolved completely after delivery and in the subsequent months. This case explores the differential diagnosis of acute headaches in pregnancy, highlighting the importance of a systematic approach where urgent diagnosis and treatment are warranted.