The most commonly used indices are the pulsatility and resistant index (PI and RI) which showed the highest predictive value ( Cnossen 2008). The rationale of using the Doppler velocimetry of uterine arteries to assess the failure of the placentation is related to fact that the lack of physiological transformation of the spiral arteries will cause high resistance to blood flow within uterus and subsequently in uterine arteries.Īt least 15 different uterine artery Doppler indices have been used to quantify the uterine arteries perfusion and predict pre‐eclampsia and IUGR ( Cnossen 2008). By studying the uterine arteries with pulse Doppler ultrasound, it is possible to assess the progressive decrease in resistance to blood flow. The blood flow from the uterine arteries to the placenta will progressively increase during that time. Physiological process of the trophoblastic invasion of spiral arteries takes place between six and 24 weeks of gestation in normal pregnancies. The measurements obtained will reflect, in any vessel studied, the cardiac contraction force, density of the blood, vessel wall elasticity, but more importantly peripheral and downstream resistance ( Owen 2001). While colour and power Doppler provide visualisation of the blood flow and its direction, pulsed Doppler allows reproducible measurements of the blood velocities. The principle can be applied using different ultrasound modalities such as continuous‐wave Doppler, pulsed‐wave Doppler, colour and power Doppler wave ( Burns 1993 Chen 1996 Owen 2001). In case of Doppler ultrasound, the emitted ultrasound frequency will change when ultrasound beam encounters moving blood. This physical principle explains the observed change in wave frequency relative to the speed of a moving object. The failure to undergo these physiologic vascular changes has been associated not just with pre‐eclampsia ( Brosens 1972 Khong 1991 Sibai 2005 Von Dadelszen 2002) and intrauterine growth restriction (IUGR) ( Bernstein 2000 Fisk 2001 Khong 1991), but also with other maternal diseases such as diabetes mellitus ( Khong 1991), lupus erythematosus ( Nayar 1996), antiphospholipid antibody syndrome ( Levy 1998) and others ( Barker 2004).ĭoppler ultrasound velocimetry uses the Doppler principle to analyse the properties of the blood flow in a vessel of interest. As the trophoblastic invasion continues during the first half of pregnancy, the resistance to the blood flow in the uterine arteries progressively decreases. The most important change, but not the only one, is replacement of the muscular and elastic arterial layer by collagen ( Espinoza 2006). During the first and second trimester of pregnancy, trophoblast invades the spiral arteries ‐ a process that is fundamental for normal placentation. Once the arterial vessels reach myometrium, they divide into arcuate arteries, then into the radial arteries which ultimately branch into the spiral arteries. The blood supply to the uterus is provided mainly by the uterine arteries and also by the ovarian arteries. More research is needed on this important aspect of care. ![]() We did not find any studies in the first trimester of pregnancy or in women at risk of high blood pressure disorders. ![]() However, more data would be needed to show whether maternal Doppler is effective, or not, for improving outcomes. We identified no improvements for the baby or the mother. The studies were of good quality but small in size. ![]() All the women were in the second trimester of pregnancy and at low risk for hypertensive disorders. The review of randomised controlled trials of routine Doppler ultrasound of the uterus or placenta identified two studies involving 4993 women. This screening offers a potential for benefit, but also a possibility of unnecessary interventions and adverse effects. We also choose to look at women with low‐risk and high‐risk pregnancies, and in their first or second trimesters. Other reviews have looked at the use of Doppler ultrasound on the babies' vessels (fetal and umbilical Doppler ultrasound). If abnormal blood circulation is identified, then it is possible that medical interventions might improve outcomes. We set out to assess the value of using Doppler ultrasound of the mother's uterus or placenta (utero‐placental Doppler ultrasound) as a screening tool. It is used in pregnancy to study blood circulation in the baby, the mother's uterus and the placenta. Doppler ultrasound uses sound waves to detect the movement of blood in blood vessels. One of the main aims of routine antenatal care is to identify mothers or babies at risk of adverse outcomes.
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