LIMITED CLINICAL UTILITY OF MIDTRIMESTER FETAL MORPHOMETRIC PERCENTILE RANKINGS IN SCREENING FOR BIRTH-WEIGHT ABNORMALITIES

OBJECTIVE: Our purpose was to determine whether midtrimester fetal ult rasonographic morphometric percentile rankings are sensitive screening tests for preterm labor or birth weight abnormalities. STUDY DESIGN: Stepwise multiple regression and chi(2) analysis were used to identify midtrimester fetal measurements predicting birth weight and gestation al age. Receiver-operator characteristic curves were used to evaluate abdominal circumference percentiles as a test for large-for-gestationa l-age and small-for-gestational-age infants. RESULTS: Extremes in abdo minal circumference and head measurement percentiles were associated w ith large-and small-for gestational-age infants but not with preterm d elivery. Abdominal circumference predicted birth weight in regression analysis; however receiver-operator characteristic curves showed abdom inal circumference percentiles to be poor screening tests for large-or small-for-gestational-age infants. The positive predictive value of 1 0th and 90th abdominal circumference percentiles for small-and large-f or-gestational-age infants was <20%. CONCLUSION: Midtrimester percenti le rankings offer no clear benefit in targeting fetuses with potential birth weight abnormalities or risk of preterm delivery and may provid e clinically misleading information.