Pathologists routinely use fetal foot length (FFL) to estimate the gestational ages (GA) of aborted fetuses. However, there is no standard formula. We aimed to develop an updated FFL-to-GA reference range from patient reported last menstrual period (LMP), ultrasound estimate, and best estimate for GA based on American College of Obstetricians and Gynecologists’ criteria in our patient population. After determining a reference range, we compared our measurements to those of previously published, commonly referenced FFL tables, which may not represent the ethnic diversity, or increasing BMI of current patient populations.METHODS:
Retrospective chart review of 628 dilation and evacuation (D&E) clinical records and procedure pathology reports from October 2012 to December 2014 in Honolulu, HI.RESULTS:
A linear relationship exists between FFL and GA in our population. Linear regression analysis of three pregnancy dating methods demonstrated that ultrasound derived dating provided the best-fit regression formula: FFL (mm) =496*(GA in days)-34.53 with an R2 value of .916. Patient race/ethnicity and BMI did not affect these equations in regression analysis. Our mean FFL differed from historically referenced ranges by .36-3.92mm, dependent on GA. Our FFL by GA was similar to ranges more recently endorsed by the National Abortion Federation despite differences in population racial and ethnic backgrounds.CONCLUSION:
If post-abortion FFL measurement is utilized for GA estimation, then updated, modern ranges should be referenced to better reflect the diversity of abortion patients nationwide.