Size of the fetus is 20 mm, then by the
rule of Hasse’s, what is the gestational
age of the fetus?
a) 2 weeks
b) 4 weeks
c) 6 weeks
d) 8 weeks
Correct Answer - C
Ans. is ‘c’ i.e.,6 weeks
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. Up to
5th month of gestation, length of the foetus in cm is square of the
month of gestation and beyond 5 months, length in cm is 5 times the
month of gestation.
Length in cm = (month of pregnancy) → upto 5 months
Length in cm = month of pregnancy → after 5 months
In this question :
Length in cm = (month of pregnancy)2
2 = (month of pregnancy) → (Note : 20mm = 2cm)
Month of pregnancy = 14 months or 6 weeks.