We combined two ultrasound techniques to develop a safe, non-invasive, transcutaneous method of observing the circulation in the umbilical arteries and vein in the fetus. The umbilical cord can be located by standard echo ultrasound procedures, and this information can be used to direct a Doppler ultrasound beam on to the vessels in the cord. The signals can be heard through audio headphones or recorded on a tape recorder and spectrum-analysed. The method was successful in each of 20 patients examined, whose pregnancies ranged from 12 to 40 weeks' gestational age, and was suitable for outpatient use. It should be useful in assessing such conditions as pre-eclampsia and intrauterine growth retardation. FIG 1-B-scan showing umbilical cord (UC) of 12-week-old fetus and displaying the echoscan depth-markers (EM).

Summary A combination of pulsed echo and continuous wave Doppler ultrasound was used to obtain blood flow velocity signals from the umbilical arteries of 18 normal patients from the 16th until the 40th week of pregnancy. Audio frequency analysis of these signals yielded fetal blood velocity waveforms. Analysis of these waveforms demonstrated that the placenta is an organ of low vascular resistance and that placental resistance to blood flow declines with advancing gestational age in normal pregnancy.

The fetal crown-rump length (CRL) was measured by means of pulsed ultrasound, and the normal values between 47 and 101 days from the onset of the last menstrual period were determined from cross-sectional data in 253 patients. For any given CRL, the range was found to be within three days of the menstrual age with a maximum variation for a given occasion of three days. Detailed statistical analysis showed that the acceleration in the rate of change in the CRL was a constant and that the intrapatient variability, where measured, was low. A close correlation between the measurement and the date of ovulation was demonstrated in a further 40 patients. 417 16

Crown-rump lengths determined ultrasonically in vivo and in utero in cases of known postovulatory age (33-86 days) agree well with those in length/age tables in current embryological usage. Within the embryonic period proper, however, for a given age, the ultrasonic lengths are usually 1 to 5 mm longer than those of fixed specimens. The probable reasons for this are discussed.

SUMMARY The cerebral circulation of 25 normal term infants was investigated using continuous wave Doppler ultrasound. Serial blood flow velocity signals were obtained from the common carotid and anterior cerebral arteries during the first week of life. The records were processed using a frequency spectrum analyser to provide cerebral blood velocity waveforms. The pulsatility index (PI), A/B ratio, and rise and fall slope of the waveforms were calculated. The results indicated that cerebrovascular resistance was raised appreciably on day 1 of life compared with later in the first week. In 18 of 25 infants (72 %) there was no continuous carotid blood flow in the first hours of life. We suggest that the human cerebral circulation adapts to the process of birth in a similar fashion to that of animal models.Intracranial haemorrhage and ischaemic hypoxic encephalopathy are major causes of mortality and morbidity in the newborn infant. The pathogenesis of these disorders is not, however, clearly understood and there is little information concerning cerebral blood flow.' Much of the data on cerebral circulation has been inferred from animal experiments,2 3 or has been obtained by venous occlusion plethysmography4 or by the use of isotopes.5 More recently Bada et al.6 used Doppler ultrasound to study the pulsatile flow in theanterior cerebral arteries of the newborn infant and this technique has since been employed to assess infants with hydrocephalus7 and patent ductus arteriosus.8 9 The pattern of cerebral blood flow in normal or distressed newborn infants has yet, however, to be fully elucidated. We used continuous wave Doppler ultrasound with frequency spectrum analysis to evaluate red blood cell velocity in the cerebral circulation of healthy newborn infants during the first week of life. Patients and methodsTwenty five normal term infants with a mean birthweight of 3380 g (range 2750-4420 g) and a mean gestational age of 40.0 weeks (range 37.6-41*9 weeks) were examined. In all these babies, who presented vertex and were delivered without assistance, labour started spontaneously and was not accelerated. The infants were studied twice on the first day of life and the first examination was within 6 hours of birth. Further assessments took place on days 2, 3, and 5. The examinations were carried out by the same person (P G) at least 1 hour after a feed apart from those performed on day 1. The following technique was used: the tip of a pencil probe of a bidirectional Doppler instrument (Medasonics Versatone D-9) operating at a frequency of 5 MHz was placed on the skin over each common carotid artery at the base of the neck using a water based gel as a coupling medium. The Doppler signals were monitored through headphones and the probe was manipulated to obtain the best quality signals which were then recorded on magnetic tape. The probe was then placed in a similar fashion over the anterior cerebral arteries as they course along the longitudinal fissure.Audiofrequency analysis of the Doppler signals was performed with a...