<prompt> Hesss rule is useful for detection of:Fetal weightFetal ageFetal lengthFetal movements  <response>: Ans. b Fetal age. Ref. Textbook of FMT by Parikh 6th ed. 5.67Hesss rule CRL of embryo or fetus is based on Hesss rule, which states that square root of length of fetus in cm gives approximate age of fetus in months in first 5 months of pregnancy. After 5 months it is length in cm5 age months. 