A female infant was born at IUP 41+1 wks to a nulliparous woman by normal vaginal delivery. Physical examination at delivery was notable for a birth weight of 2,560 gm, consistent with post term SGA and IUGR. She had no trauma history nor vacuum delivery history but gradually developed a huge cephalhematoma (8 x 7 cm sized) on right parietotemporal area on 5 days after birth. Thrombocytopenia (platelet count 63,000/μL) was checked on initial admission. The coagulation factors and platelet function test were in normal range. She had no family history of coagulation disorder. The infant had wide set eyes, short and upturned nose, slightly triangular face, and camptodactly. Her fourth right toe was thinner than other toes and her third and fourth left fingers bent and won\'t open with little force. Abdomen USG and kidney USG were done and there was no abnormality. Brain USG and MRI was done and MR findings said a huge variable stages of hemorrhage in the Rt parietal bone, suggesting cephalhematoma. We had gone through G-scanning and 11q24 deletion was noted. Finally 46,XX,del(11)(q23.3) was checked at karyotyping, consistent with Jacobsen syndrome. She underwent aspiration for large cephalhematoma and omphalodystrophy was spontaneously done at her day of life 22. Echocardiogram will be done for checking probable cardiac problems and we consulted pediatric orthopedics for her skeletal problem. She is now 3 months old and is visiting pediatric rehabilitation clinic regularly. We will observe her development for any signs of delayed milestone. Her platelets remain persistently (platelet count 63,000/μL → 64,000/μL → 100,000/μL → 115,000/μL → 96,000/μL).