Fetal and umbilical flow velocity waveforms between 10-16 weeks' gestation: a preliminary study

Area of Science:

• Perinatology
• Fetal Physiology
• Vascular Biology

Background:

• Assessing early fetal circulatory development is crucial for understanding normal pregnancy.
• Doppler velocimetry provides non-invasive insights into fetal hemodynamics.

Purpose of the Study:

• To characterize maximal flow velocity waveforms in key fetal arteries during early gestation (10-16 weeks).
• To investigate changes in fetal and umbilical placental vascular resistance during the first and early second trimesters.

Main Methods:

• Cross-sectional study involving 77 normal singleton pregnancies.
• Doppler ultrasound was used to record flow velocity waveforms in the umbilical artery, fetal descending aorta, and fetal intracerebral arteries.
• Analysis of end-diastolic flow and pulsatility index at different gestational ages.

Main Results:

• Absence of end-diastolic flow in the fetal descending aorta and umbilical artery was noted in 10-12 week gestations.
• End-diastolic flow was present in 58% of intracerebral artery waveforms at 10-12 weeks.
• A significant decrease in pulsatility index was observed with advancing gestational age across all measured sites.
• No correlation was found between waveform changes and fetal heart rate.

Conclusions:

• Early fetal circulation demonstrates evolving diastolic filling patterns.
• Decreasing pulsatility index suggests a reduction in vascular resistance in both the fetoplacental and fetal central circulation during late first and early second trimesters.
• These findings provide normative data for early pregnancy hemodynamic assessment.