The conducting gel is non-staining but may feel slightly cold and wet.
Such measurements form the cornerstone in the assessment of gestational age, size and growth in the fetus.
Dating with the CRL can be within 3-4 days of the last menstrual period.
(Table) An important point to note is that when the due date has been set by an accurately measured CRL, it should not be changed by a subsequent scan.
Fetal body measurements reflect the gestational age of the fetus. In patients with uncertain last menstrual periods, such measurements must be made as early as possible in pregnancy to arrive at a correct dating for the patient. In the latter part of pregnancy measuring body parameters will allow assessment of the size and growth of the fetus and will greatly assist in the diagnosis and management of intrauterine growth retardation (IUGR).
a) The Crown-rump length (CRL) This measurement can be made between 7 to 13 weeks and gives very accurate estimation of the gestational age.