Rule of Haase is used to calculate -

Ans. is 'a' i.e., Age of fetus Rule of Haaseo Hess's rule (Haase's rule) : It is a rough method for calculating the age of fetus by measuring the length from crown to heel.o Upto 5th month of gestation, length of foetus in cm is square of the month of gestation and beyound 5 months, length in cm is 5 times the month of gestation.