At what gestational age range is the crown-rump length most accurate for determining the estimated date of birth (EDB)?

The crown-rump length (CRL) is a crucial measurement in early pregnancy to help estimate the date of birth (EDB). Between 6 and 10 weeks of gestation, the CRL is particularly reliable because this is when the embryo is still relatively small and grows rapidly, resulting in consistent and predictable growth patterns.

During this gestational age range, the CRL measurement has a strong correlation with gestational age due to the growth characteristics of the embryo. Measurements taken in this period can typically vary by only a few days, making it an optimal time for determining the EDB. This precision is essential for appropriate prenatal care and to help avoid complications associated with incorrect dating, such as preterm or post-term deliveries.

In contrast, measurements taken outside this range, such as at 4 to 6 weeks, may be less accurate due to the embryo's smaller size and variability in early pregnancy development. At 12 to 18 weeks, while still useful, the growth rate begins to slow down, which can lead to wider variations in measurements. Beyond 20 weeks, the CRL is less effective for dating due to the growth rate differences from week to week and the influence of other factors on fetal growth patterns. Therefore, the most