Intracerebral, aortic, and umbilical artery flow velocity waveforms in the late-first-trimester fetus.

OBJECTIVES

Our objectives were to determine the success rate in obtaining flow velocity waveforms in the first-trimester fetal circulation and to establish possible preferential flow to the fetal cerebrum at this early stage of gestation.

STUDY

DESIGN

Flow velocity waveform recordings were made in the umbilical artery, fetal descending aorta, and fetal intracerebral arteries in 30 normal pregnancies between 11 and 13 weeks of gestation.

RESULTS

Technically acceptable waveforms were obtained from the descending aorta in 15 fetuses, from the intracerebral circulation in 17 fetuses, and from the umbilical artery in all 30 fetuses. Absent end-diastolic velocities in the descending aorta and umbilical artery were associated with forward flow throughout the cardia cycle in intracerebral arteries.

CONCLUSION

A relatively low cerebral vascular resistance in the late-first-trimester normal fetus is suggested.