Uterine Artery Color Doppler Velocimetry in Primigravidas (First Pregnancy)

Introduction:

Pregnancy is considered an important event in a woman’s life both physically and psychologically. It is regarded as a start of a new life for women. That is why being pregnant for the first time is crucial. The first pregnancy is termed primigravida. This is also a challenging situation medically, as both mother and the baby undergo a series of changes over time. Assessment of the medical conditions of the mother and the baby is of utmost importance. As this will help evaluate potential risk factors related to pregnancy. Different diagnostic tests are necessary to avert any potential complications of first-time pregnancy.

What Is Primigravida?

The first pregnancy of a woman is known as primigravida. Assessment of potential risk factors is necessary for such conditions. Proper medical history of such patients includes:

1. Age of the Patient: Age is an important indicator of risk factors, as pregnancy at a young or very late can be complicated.

2. Weight: It indicates nutrition and pregnancy complications are more for obese persons.

3. Obstetric History: Previous history of complications and miscarriage.

4. Medical History: The mother's medical history regarding diseases like hormonal problems and hypertension is important.

Apart from this, different diagnostic tests like doppler ultrasound are necessary. These tests help to access various conditions like fetal position, placental condition, and fetal growth.

What Is Uterine Artery Color Doppler Velocimetry?

Color doppler is a noninvasive method to diagnose the nature of the blood flow. This method transmits pulses (sound waves) to determine blood movement. Echoes from moving scatterers exhibit a slight difference in the time for the signal to be returned to the receiver. These differences are known as phase shifts from which the ‘Doppler frequency’ is obtained. These color frequencies provide information about blood flow.

Uterine blood supply is an important factor for pregnancy. This provides the necessary nutrition to fetal blood and aids in fetal growth. Also, necessary oxygenation is provided by these vessels. That is why examining uterine artery velocimetry is necessary to exclude complications.

What Is the Technique for Uterine Artery Doppler?

Doppler velocimetry in the cervicocorporeal junction is done either through a trans-abdominal or trans-vaginal approach. During the procedure, the displayed thermal index should be ≤ 1.0, and the exposure time should be kept as short as possible, usually no longer than 5 to 10 min. During the procedure, the following things are followed:

• This is performed only when the fetal age is 11 to 13 + 6 weeks.

• During the procedure, the thermal index should be ≤ 1.0, and the exposure time should be kept as short as possible, usually no longer than 5 to 10 min.

• The mother is asked to hold her breath for a brief period during the procedure.

• The exposure angle should be aligned with the direction of blood flow. Incorrect angulation of 10 degrees corresponds to a two percent error in the velocity, whilst an angle of 20 degrees corresponds to a six percent error.

• The analysis starts relatively with the doppler gate (wide area of interest) to ensure the recording of maximum velocities during the entire pulse. A relatively small doppler gate is used if other blood vessels produce any interferences.

• The flow velocity scales or pulse repetition frequency (PRF) should be adjusted according to the vessel studied. A low-velocity scale is used for visualization and accurate measurement of low-velocity flow. Otherwise, the mismatch will procedure aliasing (new frequencies appearing in the sampled signal after reconstruction).

1. First-Trimester Uterine Artery Evaluation:

• For the trans-abdominal technique, a mid-sagittal section of the uterus is obtained, and the cervical canal is identified.

• The probe is then moved laterally until the paracervical vascular plexus is seen.

• Color doppler is turned on to identify the uterine artery.

• Measurements are taken before the area where the uterine artery branches into the arcuate arteries.

• The transvaginal approach is made on an empty stomach, and the patient is placed in dorsal lithotomy (feet placed at or the same level as the hips).

• For the transvaginal approach, the probe is placed in the anterior fornix (a spot located t the top of the vaginal wall) and moved laterally to visualize the paracervical vascular plexus.

2. Second- and Third-Trimester Uterine Artery Evaluation:

• For trans-abdominal approaches, the probe is placed longitudinally in the lower lateral quadrant of the abdomen, angled medially in the parasagittal plane. With the advancement in the pregnancy period, dextrorotation of the uterus causes a change in the position of the right and left uterine arteries.

• The principle for the transvaginal approach is the same as the first trimester.

What Are Its Clinical Significance?

1. The umbilical artery's blood flow is first evaluated among fetal blood vessels. The ideal flow velocity shows a characteristic saw-tooth appearance of arterial flow in one direction and continuous umbilical venous blood flow in the other.

2. Different views, like the abdominal and four-chamber, are used to measure fetal cardiac flow. In the abdominal view, the position of the aorta and inferior vena cava are first checked. Detection of numerous severe heart defects can be checked using the four-chamber view. Parameters used in such cases are

• Peak Velocity: Maximum blood velocity at a given time.

• Time to Peak Velocity: It denotes the acceleration time, the time interval between the onset of the waveform and its peak.

• Calculation of ventricular ejection force (measurement of the pumping efficiency of the blood).

3.The normal blood flow of the umbilical vein shows continuous forward flow without pulsations in the first trimester.

4. The cerebroplacental doppler ratio (CPR) is calculated from the blood flow. This indicator is used to measure arterial redistribution seen in hypoxia. Also, the increased blood supply to the brain, heart, and adrenals and a simultaneous reduction in perfusion is seen in hypoxic conditions.

5. Resistance and perfusion indices are calculated to determine risk factors for pregnancy hypoxia and fetal growth restrictions. The presence of a diastolic notch is an indicator of pregnancy hypoxia. A perfusion index greater than 1.45 in the second trimester indicates preeclampsia (high blood pressure in pregnancy).

Conclusion:

Women pregnant for the first time need extra care and protection. Assessment of medical conditions is needed to identify potential risk factors. Uterine artery color doppler velocimetry is a useful diagnostic to evaluate the condition of the mother and fetus. Growth anomalies and cardiac problems of the fetus can be identified before birth. Medical conditions like pregnancy hypertension can also be identified beforehand using this method. Moreover, this is a relatively economical diagnostic aid used in developing countries.