This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
When does switchover from fetal to adult hemoglobin synthesis begin - 
Select and explain. 
A. 14 weeks gestation, B. 30 weeks gestation, C. 36 weeks gestation, D. 7-10 days postnatal
C: 36 weeks gestation
Answer: C: 36 weeks gestation 
Explanation: Ans. is 'c' i.e., 36 weeks gestationFetal Hb (a272)Adults Hb (a2o During the initial fetal life, the major hemoglobin synthesized in the body is fetal hemoglobin, because in fetus, the chain synthesized predominantly is the 7 chain.13 chain is present in only trace amount in early embryosThe rate of synthesis of y and 13 chains and the amount of HbA and HbF are inversely related during intrauterine stage.o As the age of the fetus increases, the synthesis of 13 chains and the amount of adult hemoglobin in the blood increaseso At 36 weeks of gestational age the rate of synthesis of 13 chain exceeds that of y chain. This is called switch over.