A revisit of the fetal foot length and fetal measurements in early pregnancy sonography.

OBJECTIVES: To present the fetal measurements in relation to the foot length at 10-16 weeks gestation on antenatal ultrasound.

MATERIALS AND METHODS: We reviewed the fetal measurements in 47 scans performed at 10-16 weeks gestation in women attending routine antenatal care. The fetal measurements and measurement ratios were examined in relation to the foot length.

RESULTS: The fetal biparietal diameter, head circumference, abdominal circumference, femur length and foot length increase linearly with the gestational age at 10-16 weeks gestation. The correlation between fetal foot length and fetal biparietal diameter, head circumference, abdominal circumference and femur length are better than with the crown rump length. The femur length to foot length ratio and the femur length to abdominal circumference ratios increase with the gestational age in an inverse relationship throughout the same period.

CONCLUSION: Fetal foot length is an accurate estimate of the gestational age in early pregnancy. Compared with crown rump length, the correlation between foot length and other fetal measurements is better. The fetal measurements ratios are gestational age dependent between 10-16 weeks. Gestational age specific ratio should be used in this period.