Fetal foot length as a predictor of gestational age.

Ultrasonographic measurement of fetal foot length is useful in the assessment of gestational age. Two hundred twenty-three postpartum and 224 ultrasonographic measurements were performed between 11 and 43 weeks' gestation; 207 postpartum and 160 ultrasonographic measurements met our requirements of secure dates and no physical anomaly or maternal disease. Mean foot length at each week of gestation compared favorably with Streeter's data, based on pathologic specimens, described in 1920. Comparison of curvilinear regression of foot length versus gestational age demonstrated a strong correlation with an R2 value of 0.981; 95% confidence intervals at each week compared favorably with both biparietal diameter and femur length data. Fetal foot length is a reliable parameter for use in the assessment of gestational age and is particularly useful when other parameters do not accurately predict gestational age, for example, hydrocephalus, anencephaly, short limb dysplasia.