This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous (Gynae), Subject name: Gynaecology & Obstetrics
A 2-hour-old neonate born by normal vaginal delivery has a scalp swelling, with normal cry and activity. What is the probable cause? 
Select and explain. 
A. Serosanguineous extra periosteal fluid, B. Focal sub-aponeurotic blood collection, C. Chignon, D. Depressed skull fracture
A: Serosanguineous extra periosteal fluid
Answer: A: Serosanguineous extra periosteal fluid 
Explanation: Ans. (a) Serosanguineous extra periosteal fluid.* The reason why this skull looks asymmetrical is due to moulding. This is a caput succedaneum, where there is a serosanguineous subcutaneous extra periosteal fluid collection with poorly defined margins caused by pressure of presenting part of skull against the dilating cervix. The caput succedaneum extends across the midline, crossing over suture lines and resolves over few days. * Cephalhematoma takes >24 hours to develop and is a focal sub-periosteal bleeding. On resolution which may take weeks it may harden followed by softening from the center. It is associated with instrumentational delivery or prolonged labor which are not given in the history.* Chignon is seen after vacuum extraction and sometimes complicated by sub aponeurotic hemorrhage.