Background: The cornerstone of the obstetrician's capacity to successfully manage prenatal care is essential to prenatal testing and successful planning for appropriate treatment or intervention. [1] Menstrual irregularities, lactational amenorrhea, oral contraceptive failure, bleeding in the first trimester, and delayed conception may further affect the ability to accurately calculate GA from the date of LMP. When an early termination is required as soon as the foetus reaches maturity, such as in the case of pre-eclampsia, severe intrauterine growth retardation (IUGR), diabetes, placenta praevia, an accurate GA is crucial. Accurate GA estimation is also required when specific tests, including as chorionic villus sampling, amniotic fluid and serum testing, and foetal therapy planning, must be carried out. [2] Estimating gestational age from an early measurement of crown rump length in first trimester is accurate, however we are often faced with patients who seek late prenatal care and who have no information about their last menstrual period or when conception occurred. The parameters used in second and third trimester are BPD, HC, AC, FL and combination of them. Foetal kidney length shows no significant change with any underlying medical condition. Therefore, its length can be used as an additional measurement of foetal growth. This measurement is easy to take and can therefore be easily used for dating pregnancies after 20 weeks of gestation, particularly when measurements of biparietal diameter and head circumference are difficult.