This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: New born infants, Subject name: Pediatrics
Reflex which is not present in child at bih is 
Select and explain. 
A. Moro's reflex, B. Symmetric tonic neck reflex, C. Crossed extensor reflex, D. Asymmetric tonic neck reflex
B: Symmetric tonic neck reflex
Answer: B: Symmetric tonic neck reflex 
Explanation: Symmetric tonic neck reflex appears by 4-6 months and disappears by 8 - 12 months. Moro&;s reflex - hand opening appears by 28 wks, extension and abduction of the upper extremities by 32 wks and anterior flexion by 37 wks of intrauterine life and disappears by 3 - 6 months after bih. Asymmetric tonic neck reflex appears by 35 wks of intrauterine life and disappears by 4 - 6 months after bih. Crossed extension response begins at 28 weeks gestation and disappears by 1-2 month. Reference : page 142 Ghai Essential Pediatrics 8th edition and page 15 Paediatric Clinical examination A Santhosh Kumar