title: Continuous wave Doppler flow velocity waveforms from the umbilical artery in normal pregnancy.
abstract: The objective was to establish a normal reference range of the indices of umbilical artery waveforms using continuous wave doppler ultrasound. A prospective longitudinal study was made of 85 uncomplicated singleton pregnancies between 16 and 40 weeks gestation (783 recordings). Pulsatility Index (P.I.), Resistance Index (R.I.) and A/B ratio were measured at each visit. The mothers all delivered normal healthy infants weighing more than the 10th centile for gestational age. All three indices have a positively skewed frequency distribution, a factor not generally appreciated until recently and the ranges are therefore described using non-parametric statistics. Placental resistance decreases as term approaches, the 50% PI at 16 weeks was 2.06, at 32 weeks was 1.08 and at 40 weeks was 0.85. The results show a comprehensive reference of normal values and provides a sound basis for the further study of abnormal pregnancy. It represents the largest published study of its type using continuous wave Doppler.
authors.affiliation: Department of Obstetrics and Gynaecology, Royal Maternity Hospital, Belfast, N. Ireland.
authors.forename: P
authors.initials: P
authors.lastname: Fogarty
authors.forename: B
authors.initials: B
authors.lastname: Beattie
authors.forename: A
authors.initials: A
authors.lastname: Harper
authors.forename: J
authors.initials: J
authors.lastname: Dornan
mesh_terms: D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity; D005260:Female; D005312:Fetal Blood; D005865:Gestational Age; D006801:Humans; D008137:Longitudinal Studies; D011247:Pregnancy; D011446:Prospective Studies; D012016:Reference Values; D014465:Ultrasonics; D014469:Umbilical Arteries / Q000502:physiology*