Volume 165 Number 4, Part 1 plicated term vaginal deliveries. AM ] OBSTET GVNECOL 1985; 151 :798-80 1. 18. Thorp ]A, Sampson ]E, Parisi VM, Creasy RK. Routine umbilical cord gas determinations. AM] OBSTET GVNECOL 1989;161:600-5. 19. Gilstrap LC, Leveno K], Burris], Williams ML, Little BB. Diagnosis of birth asphyxia on the basis of fetal pH, Apgar score, and newborn cerebral dysfunction. AM] OBSTET GVNECOL 1989; 161 :825-30. Meconium and birth asphyxia 20. Freeman ]M, Nelson KB. Intrapartum asphyxia and ce- rebral palsy. Pediatrics 1988;82:240-4. 21. Weitzner ]S, Strassner HT, Rawlins RG, et al. Objective assessment of meconium content of amniotic fluid. Obstet Gynecol 1990;76: 1143-4. 22. Yeomans ER, Gilstrap LC, Leveno K], Burris ]S. Meco- nium in the amniotic fluid and fetal acid-base status. Ob- stet Gynecol 1989;73: 175-8. The relationship between umbilical artery Doppler velocimetry and fetal biometry William E. Scorza, MD, Deborah Nardi, RT(R), RDMS, Anthony M. Vintzileos, MD, Alfred D. Fleming, MD, John F. Rodis, MD, and Winston A. Campbell, MD Farmington, Connecticut The relationship between peak-systolic/ end-diastolic ratio of the umbilical artery waveform and fetal biometry was studied in 127 uncomplicated pregnancies with established dates between 20 and 40 weeks' gestation. At each ultrasonographic examination fetal biometry included measurement of the biparietal diameter, head circumference, abdominal circumference, and femur length. The peak-systolic/end-diastolic ratio was measured by either a continuous or a pulsed-wave method. There were significant linear negative correlations between all the biometric parameters, as well as between the ultrasonographically estimated fetal weight and peak-systolic/end-diastolic ratio. Of the individual ultrasonographic parameters the femur length (for gestations <30 weeks) and the abdominal circumference (for gestations 2:30 weeks) were found to be best correlated with the peak-systolic/end-diastolic ratio. Regression curves, including the 10th and the 90th percentile, were developed between each biometric parameter (biparietal diameter, head circumference, abdominal circumference, and femur length), as well as between estimated fetal weight and peak-systolic/end-diastolic ratio. The estimated fetal weight nomogram had the best sensitivity (48%) in predicting intrauterine growth retardation. These nomograms should prove most useful in assessing downstream placental vascular resistance in high-risk patients with unknown dates. (AM J OBSTET GVNECOL 1991 ;165:1013-9.) Key words: Umbilical artery velocimetry, fetal biometry Continuous or pulsed-wave Doppler ultrasonogra- phy of the fetal umbilical artery has been increasingly used in clinical obstetrics in the management of high- risk pregnancy. I·' The measurement of the peak-sys- tolic/ end-diastolic ratio of the umbilical artery flow ve- locity waveform is the most commonly used method. Abnormal ratios have been associated with an increased incidence of neonatal morbidity, mortality, and intra- uterine growth retardation. 1 . 5 The abnormal wave- From the Division of Maternal-Fetal Medicine, Department of Ob- stetrics and Gynecology, University of Connecticut Health Center. Presented at the Eleventh Annual Meeting of the Society of Perinatal Obstetricians, San Francisco, California, january 28-February 2, 1991. Reprint requests: William E. Scorza, MD, Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, Mount Sinai Hospital, 500 Blue Hills Ave., Hartford, CT 06112. 6/6/30898 forms are believed to be the result of increased down- stream placental vascular resistance and therefore of impaired placental perfusion. 6 The proper use of the umbilical artery peak-systolic/ end-diastolic ratio, how- ever, requires knowledge of the length of gestation, which is unknown or unavailable in 20% to 40% of pregnant patients. 7 When the last menstrual period is unknown or uncertain, extrapolation of gestational age on the basis of fetal biometric data may lead to erro- neous interpretation of the peak-systolic/ end-diastolic ratio results, because there are no data regarding the relationship between the umbilical artery peak-sys- tolic/ end-diastolic ratio and fetal biometry. Therefore the purpose of the present report was: (1) to study the relationships and generate regression curves between the peak-systolic/ end-diastolic ratio and the most com- monly used fetal biometric parameters (biparietal di- 1013