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: Social & Preventive Medicine
Which one of the following is categorised as a high 
Select and explain. 
A. Birth order 3, B. Maternal height 150 cm, C. Twins pregnancy, D. Blood group AB +ve
C: Twins pregnancy
Answer: C: Twins pregnancy 
Explanation: None