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: Gynaecology & Obstetrics
Hasse’s formula used in pregnancy to? 
Select and explain. 
A. Identify sex age, B. Identify fetal blood group, C. Estimate fetal age, D. Identify fetal congenital malformations
C: Estimate fetal age
Answer: C: Estimate fetal age 
Explanation: Hasse’s formula If the crown-heel length is known then the intrauterine age of the fetus is calculated as:
If CH length is up to 25 cm then IU age = Square root of CH length If the CH length is > 25 cm then IU age = 1/5 of CH length