Fetal foot length.

Data on fetal weight (FW) and two foot measurements, heel-toe length (HTL) and the distance between the heel and the point of maximal convexity of the metatarsophalangeal crease (HML), are analysed. Analysis shows that the regression of FW on each of the foot measurements is curvilinear, that there is strong correlation between the variables, and that HML is a better guide to FW than HTL. Simple formulas are presented for calculating FW from foot measurements. A comparison of the regression of HTL on FW in present-day fetuses and those in Streeter's study (1920) shows that despite a significant secular trend for birth weight to rise, the HTL/FW relationship is essentially unchanged.