What is the normal range for humerus length at 27 weeks?

At 27 weeks of gestation, the normal range for fetal humeral length is approximately 4.21–5.03 cm. This value may vary individually due to factors such as genetics and nutrition. Slight deviations from the normal range in a single measurement do not require excessive concern and should be evaluated in conjunction with the overall growth and development of the fetus. Detailed analysis is as follows:

Humeral length is an important indicator for assessing fetal upper limb skeletal development. At 27 weeks of pregnancy, the fetus is transitioning from the second to the third trimester, during which skeletal growth proceeds at a steady pace. Clinical data show that the average humeral length at this gestational age is about 4.62 cm, with variations within ±0.41 cm considered normal. Minor discrepancies in measurements can also result from technical factors such as the sonographer's technique or fetal position, all of which fall within acceptable limits.

If the measured humeral length is significantly below the lower limit, it may indicate intrauterine growth restriction or abnormal skeletal development. Conversely, values far exceeding the upper limit may suggest the possibility of a macrosomic infant. However, such assessments must be made by integrating other growth parameters—such as biparietal diameter and abdominal circumference—as well as considering the accuracy of gestational dating and prior ultrasound findings. Conclusions should not be based solely on a single measurement.

Pregnant women at 27 weeks should ensure adequate nutrition, consuming sufficient calcium- and protein-rich foods such as milk, lean meat, and soy products to support fetal skeletal development.