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Uteroplacental Doppler flow velocity waveforms in the second trimester. A complex circulation.
S Bewley1, S Campbell, D Cooper
1Department of Obstetrics and Gynaecology, King's College Hospital, Denmark Hill, London.
British Journal of Obstetrics and Gynaecology
|September 1, 1989
Summary
Continuous wave Doppler ultrasound revealed a significant decrease in uteroplacental resistance index (RI) as pregnancy progresses. Lower RI values were observed at placental sites compared to non-placental sites.
Area of Science:
- Obstetrics and Gynecology
- Fetal Medicine
- Medical Imaging
Background:
- Uteroplacental circulation is crucial for fetal development.
- Doppler ultrasound is a key tool for assessing fetal well-being.
- Establishing normal reference ranges for uteroplacental blood flow is essential.
Purpose of the Study:
- To establish reference ranges for the resistance index (RI) in uteroplacental circulation.
- To investigate changes in RI throughout early to mid-gestation (16-24 weeks).
- To compare RI values between placental and non-placental sites, and between different vascular locations.
Main Methods:
- Continuous wave Doppler ultrasound was employed.
- A cohort of 977 women was studied between 16 and 24 weeks of gestation.
- Resistance index (RI) measurements were taken from various uteroplacental and uterine arterial sites.
Main Results:
- A significant decline in RI was observed with advancing gestation.
- RI values were consistently lower at placental sites compared to non-placental sites.
- Distal 'arcuate' artery RI was lower than proximal 'uterine' artery RI.
Conclusions:
- Normal reference ranges for uteroplacental RI decrease with increasing gestational age.
- Standardized sampling sites are necessary for accurate RI assessment.
- Further research is needed to define fixed sites and account for placental site variations in normal ranges.