Aneurysmal subarachnoid hemorrhage (SAH) during pregnancy is quite rare, however it has a high maternal mortality rate. A pregnant woman in the 16th gestational week was admitted to our hospital with a drowsy level of consciousness. A brain magnetic resonance (MR) image showed hemorrhage on the prepontine cistern, and both sylvian fissures, and MR angiography and cerebral digital subtraction angiography demonstrated an aneurysm at the left posterior inferior cerebellar artery (PICA). We performed endovascular coil embolization attempting to minimize radiation exposure. She was discharged with no neurologic deficit and delivered a healthy baby by cesarean section at the 38th week of gestation. This case study reported the shortest gestational period and this is the first report on an aneurysmal rupture arising from PICA which was treated using an endovascular method. Using an appropriate technique for reduced radiation exposure to the fetus and limited alterations in maternal-fetal physiology, endovascular coil embolization could guarantee good results in treatment of aneurysmal SAH in pregnant women.