The crown-rump length measurement - ISUOG criteria and clinical practice

Significance of the crown-rump length (CRL) measurement criteria in the assessments of gestational age and actual precision in daily clinical practice.

We recruited 806 pregnant women with singleton pregnancy and history of regular menstrual periods.We analysed retrospectively CRL measurements obtained during routine first trimester scan performed between 11 + 0 and 13 + 6 weeks gestation. Gestational age was calculated using both the last menstrual period (LMP) and the CRL. The images of the CRL measurements were assessed by the expert. The visual analysis of the images in terms of meeting the five criteria recommended by the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) was performed. Statistical analysis were used to assess how the above-mentioned criteria influenced calculation of the gestational age.

The study showed 323 out of 806 of the CRL measurements (40.1%) were qualified by a specialist as accurate, 279 (34.6%) as inaccurate, and 204 (25.3%) as inaccurate, but not changing the duration of a pregnancy. With the application in the assessment of the five criteria of the ISOUG 217 (26.9%), the following results of qualification were obtained: accurate - fulfilled ≥ 4, inaccurate 341 (42.3%) - fulfilled ≤ 2, whereas inaccurate, but not changing the duration of a pregnancy 248 (30.8%) - 3 criteria fulfilled. We found that only the neutralof the fetus demonstrated a significant corellation with the assessment of the duration of a gestation.

a) the accurate audit of the CRL measurements is recommended; b) neutral position of the fetus is the most important criterion out of 5.