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Blood flow velocity waveforms from the fetal external iliac artery as a measure of lower extremity vascular
P A Stewart1, J W Wladimiroff, T Stijnen
1Department of Obstetrics & Gynaecology, Erasmus University, Rotterdam, The Netherlands.
Insights
In pregnancies, external iliac artery (EIA) and umbilical artery (UA) blood flow showed reduced resistance with gestational age. Intrauterine growth retardation (IUGR) cases exhibited elevated resistance in both EIA and UA.
Area of Science:
- Perinatology
- Fetal Medicine
- Vascular Physiology
Background:
- Fetal growth and well-being are critically dependent on placental and fetal circulation.
- Assessing vascular resistance in fetal arteries provides insights into placental function and potential fetal compromise.
Purpose of the Study:
- To evaluate blood flow velocities and vascular resistance in the external iliac artery (EIA) and umbilical artery (UA) during normal pregnancy and in cases of intrauterine growth retardation (IUGR).
- To determine the relationship between gestational age and pulsatility index (PI) in these vessels.
- To investigate the utility of EIA and UA Doppler parameters in identifying fetuses with IUGR.
Main Methods:
- Doppler ultrasound was used to record blood flow velocities in the EIA and UA of 94 normal pregnancies and 14 pregnancies with IUGR.
- Measurements were taken between 25 and 36 weeks of gestation.
- Pulsatility index (PI) was calculated for both vessels, and the EIA PI/UA PI ratio was analyzed.
Main Results:
- In normal pregnancies, PI in both EIA and UA significantly decreased with advancing gestational age, indicating reduced vascular resistance.
- The EIA PI/UA PI ratio also decreased with gestational age, suggesting greater relative vascular resistance in the lower extremities.
- Pregnancies with IUGR consistently showed PI values above the normal range (+2 SD) in both EIA and UA, signifying increased vascular resistance.
- Absent end-diastolic flow in the UA was associated with reversed end-diastolic flow in the EIA in two IUGR cases.
Conclusions:
- Doppler assessment of EIA and UA blood flow is valuable for monitoring fetal vascular resistance.
- Decreased PI with gestational age in normal pregnancy reflects normal development of lower extremity and placental vasculature.
- Elevated PI in EIA and UA is a significant indicator of increased vascular resistance in fetuses with IUGR, potentially reflecting placental insufficiency.
Abstract:
Blood flow velocities were recorded in the external iliac artery (EIA) and umbilical artery (UA) in 94 normal pregnancies and in 14 with intrauterine growth retardation (IUGR) between 25 and 36 weeks gestation. In normal pregnancy the pulsatility index (PI) in both vessels decreased significantly with advancing gestational age, reflecting a reduction in lower extremity and placental vascular resistance. The EIA PI/UA PI ratio also decreased significantly with gestational age suggesting that vascular resistance is more pronounced in the lower extremities. In the pregnancies with IUGR, PI values from both vessels were nearly always above the upper limit (+2 SD) of the normal curve reflecting increased vascular resistance at lower extremity and placental level. In two pregnancies, absent end-diastolic flow velocities in the umbilical artery were associated with reversed end-diastolic flow velocities in the external iliac artery.