Fetal clavicle length throughout gestation: a nomogram.

Area of Science:

• Obstetrics and Gynecology
• Fetal Medicine
• Diagnostic Ultrasound

Background:

• Accurate fetal biometry is crucial for monitoring pregnancy progression and detecting potential abnormalities.
• Existing nomograms for fetal clavicle length (CL) may not reflect current sonographic capabilities or population data.

Purpose of the Study:

• To develop an updated nomogram for fetal clavicle length (CL) across a wide range of gestational ages (14-42 weeks).
• To compare new CL data with historical nomograms and assess the accuracy of common rules of thumb for gestational dating.

Main Methods:

• A cross-sectional study involving 623 singleton, non-anomalous fetuses with well-established gestational dating.
• Sonographic measurements included biparietal diameter, head circumference, abdominal circumference, femur length, humerus length, and sonographically estimated fetal weight.
• Fetal clavicle length (CL) was measured, and the 5th, 50th, and 95th centiles were determined using least squares regression.

Main Results:

• Fetal clavicle length (CL) was successfully measured in 620 out of 623 fetuses.
• A strong correlation was observed between CL and other standard fetal biometric parameters (BPD, HC, AC, HL, FL, SEFW).
• The newly generated nomogram showed significantly larger CL measurements compared to a 1985 nomogram for most gestational ages.

Conclusions:

• A new, comprehensive nomogram for fetal clavicle length (CL) is proposed, reflecting advancements in ultrasound technology.
• The updated nomogram should supersede previous data due to its larger sample size and modern methodology.
• The '1 mm = 1 week' rule of thumb for gestational dating based on CL is deemed unreliable and potentially erroneous.