In the Results section of the Skupski et al1 article in the August 2017 issue (page 436), the formula used to estimate gestational age needs updating.
For simplicity of presentation, the authors reported the estimated coefficients to only a reduced number of significant digits. However, all calculations were evaluated using coefficients with much more precision. For implementation of the formula, the authors recommend that readers use the updated formula.
The original, less accurate, formula was: “…gestational age (weeks)=10.6−0.168×BPD+0.045×HC+0.03×AC+0.058×FL+0.002×BPD2+0.002×FL2+0.0005×(BPD×AC)−0.005×(BPD×FL)−0.0002×(HC×AC)+0.0008×(HC×FL)+0.0005×(AC×FL), in which BPD=biparietal diameter, HC=head circumference, AC=abdominal circumference, and FL=femur length.”
The updated, more accurate, formula is:
“…gestational age (weeks)=10.5992189734−0.1682642749×BPD+0.0451977088×HC+0.0302344331 ×AC+0.0575622626×FL+0.002497813×BPD2+0.0017031489×FL2+0.0005458077×(BPD×AC)−0.0051546864×(BPD×FL)−0.000276112×(HC×AC)+0.0007657091×(HC×FL)+0.0005523225×(AC×FL).”
1. Skupski DW, Owen J, Kim S, Fuchs KM, Albert PS, Grantz KL, et al. Estimating gestational age from ultrasound fetal biometrics. Obstet Gynecol 2017;130:433–41.