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: Physiology
Fetal erythropoietin production is inhibited by? 
Select and explain. 
A. Testosterone, B. Estrogen, C. Coisol, D. Hypoxia
B: Estrogen
Answer: B: Estrogen 
Explanation: Ans. is 'b' i.e., Estrogen Ref: Principles and practice of maternal healthThe plasma erythropoietin activity increases steadily during pregnancy.Estrogen antagonizes the erythropoietin-augmenting effect of placental lactogen.It inhibit utilization of erythropoietin by the marrow stem cells, and also impairs its production.