A 32-year-old woman was at the end of her first and-until then normal-pregnancy, when she abruptly experienced a severe neck pain. Delivery was provoked two days later but a week after she suddenly developed a left lateral medullary syndrome. Angiography disclosed a severe diffuse and irregular narrowing of both vertebral arteries in their second and third segments, typical of dissecting aneurysm. The patient was treated with heparin and made a partial recovery. A second angiography nine months later showed a normal left vertebral artery while the right one was probably occluded.