FL/ AC ratio: Poor predictor of intrauterine growth retardation

Carol B. Benson, Peter M. Doubilet, Daniel H. Saltzman, Thomas B. Jones

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Early antenatal detection of intrauterine growth retardation (IUGR) may decrease the associated perinatal morbidity and mortality. A parameter based on sonographically measured femur length (FL) and abdominal circumference (AC), expressed as FL/AC × 100 and termed the FL/AC ratio, has recently been proposed by Hadlock et al as an age-independent predictor of IUGR. We studied 285 normal and 37 IUGR fetuses to verify that the FL/AC ratio is independent of gestational age (GA) and to assess its value as a predictor of IUGR. Our results confirm that the FL/AC ratio is age-independent above 20 weeks and that its mean value differs in normal (22.4 ± 1.7) and IUGR (23.7 ± 1.4) fetuses (P<.01, t-test). Because of considerable overlap between these two groups, however, there is no cutoff value for the FL/AC ratio that yields both a high sensitivity and a high specificity, or that leads to a high positive predictive value. With a cutoff of 23.5, for example, the sensitivity is 56% and the specificity 74%, and, even assuming an IUGR prevalence rate of 10%, the likelihood of IUGR in a fetus with an FL/AC ratio above the cutoff is only 19%. We conclude that the FL/AC ratio, though an age-independent measure whose mean value differs in normal and IUGR fetuses, is not clinically useful as a predictor of IUGR.

Original languageEnglish
Pages (from-to)727-730
Number of pages4
JournalInvestigative Radiology
Volume20
Issue number7
DOIs
StatePublished - Oct 1985
Externally publishedYes

Keywords

  • Abdominal circumference
  • Femur length
  • Intrauterine growth retardation

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