Prenatal age-specific reference intervals for measuring all five digits of the fetal hand

Objective: To construct prenatal age-specific reference intervals for measurement of five digits in normal fetuses. Patients and Methods: Prospective cross-sectional study of fetuses assessed at an antenatal ultrasound unit in a university-affiliated general hospital. The study cohort comprised 302 pregnant women attending our clinic for routine fetal biometry or anomaly scan between December 1997 and June 2000. They all fulfilled the study inclusion criteria: singleton fetuses with normal anatomy, accurate gestational age and no medical complications of pregnancy. Each fetus was scanned once only and the finger measurements of one hand were obtained. Electronic calipers were placed on the outer margin of the proximal phalanx to the outer margin of the distal phalanx level. Those measurements and the relevant gestational age were registered in a computerized database. Results: The linear increase of size of each of the five fingers was plotted across the evaluated range of gestation (P < 0.001; r² between 0.85 and 0.86 for fingers I to V). Tables showing the 5th, 50th and 95th centiles of finger lengths between 14 and 27 weeks' gestation were created based on the reference interval charts. Conclusions: Second-trimester measurement of all five digits of the fetal hand is feasible. This may assist in the evaluation of fetuses that are primarily suspected of having genetic abnormalities that might be expressed by deviation in finger length.