How Many Times Ultrasound Is Done In Pregnancy?

How Many Times Ultrasound Is Done In Pregnancy
Ultrasounds are a regular part of prenatal medical care for most pregnant women, and also provide parents with their first glimpses of their developing baby. Although these photographs make for nice keepsakes, most women need very few scans, and medical guidelines firmly state that ultrasounds during pregnancy should be performed only when there is a valid medical indication.

According to the American Congress of Obstetricians and Gynecologists, there have been no reports of documented negative effects on the fetus from diagnostic ultrasound procedures. But, the ACOG discourages the use of ultrasounds for nonmedical purposes because while there are no confirmed biological effects caused by scans, there’s always a possibility that some could be identified in the future.

“2D ultrasounds are the safest radiological modality offered to pregnant women, but as with everything, should be used in moderation,” says Monica Mendiola, MD, a practicing physician in Women’s Health at Beth Israel Deaconess HealthCare-Chelsea and an instructor in Obstetrics & Gynecology at Harvard Medical School.

Most healthy women receive two ultrasound scans during pregnancy. “The first is, ideally, in the first trimester to confirm the due date, and the second is at 18-22 weeks to confirm normal anatomy and the sex of the baby,” explains Mendiola. “As long as these ultrasounds are normal and mom’s abdomen measures consistent with her gestation, then that is all most women need.” Mendiola notes that if there are any problems with these initial ultrasounds, or if there is a discrepancy in the fetus size along the way, a repeat ultrasound is warranted.

“Additionally, if moms have medical issues such as diabetes or hypertension, then they will also receive additional scans,” she says. Above content provided by Beth Israel Deaconess Medical Center. For advice about your medical care, consult your doctor.
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Do you get an ultrasound in your 3rd trimester?

Technique – The initial evaluation should commence by placing a curvilinear probe with the appropriately selected OB settings over the suprapubic area. The probe can be placed in either sagittal or transverse orientation. The probe indicator should be directed to the cephalad for the sagittal images and towards the patient’s right side for transverse images.

If a transvaginal examination is indicated, the patient should be placed in the lithotomy position. The probe should be inserted with the indicator in the vertical direction. Sagittal images are obtained by maintaining the indicator pointing towards the ceiling, while transverse imaging requires rotating the probe to have the indicator facing the patient’s right side.

Several measurements are indicated for appropriate assessment of the status of the fetus and the maternal structures, starting with the estimation of the gestational age. Gestation dating by ultrasonography may be inaccurate during the third trimester.

  • Biparietal diameter (BPD)
  • Occipitofrontal diameter (OFD)
  • Head circumference (HC)
  • Abdominal diameter (AD)
  • Abdominal circumference (AC)
  • Femur length (FL)
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On the other hand, estimation of fetal size is best performed during the third trimester. Multiple formulas have been developed to estimate fetal weight, with one of the most widely used being that of Hadlock and colleagues. Formulas that used less than three fetal body part measurements did not perform well compared to formulas that include fetal head, abdomen, and femur measurements.

However, including additional measurements in the formulas has not demonstrated increased accuracy. Frequently, fetal movement can be identified and should be documented. However, lack of fetal movement can have different significances and can be affected by the fetal sleep cycle. The fetal heart should be measured using M mode as established by As Low As Reasonably Achievable (ALARA) recommendations.

The M mode caliper should be placed over the left ventricle. By measuring the temporal distance in M mode from peak to peak, most modern ultrasound machines will be able to estimate the fetal heart rate. Care must be applied to the correct number of cycles measured since some manufacturers will require two cycles to be measured, and some only one.

A normal heart rate is between 110 and 160 beats per minute. Further discussion about abnormal findings is discussed below. Evaluating the fetal lie is of paramount importance, especially as the term date approaches. First, the fetal head is identified, followed by the direction of the hyperechoic fetal spine.

If the fetal head is closer to the cervix, this is described as cephalad. The laterality of the spine is also essential, and it is always described based on the mother’s orientation. On the other hand, when the head is more cephalad to the mother, it is considered a breech presentation.

The specific type of breech presentation should be evaluated as frank, complete, or footling. The fetal anatomy should be evaluated for any apparent abnormalities. The laterality of all anatomic structures visualized should be noted. The fetal head and its general should be examined for symmetry. Intracranial anatomical structures should be visible, including the cerebellum, cavum septum pellucidum, and ventricles.

The inability to identify any of these structures warrants further investigation. The probe should be optimized to assess the heart’s movement, position, and orientation in detail. During the third trimester, the four heart chambers should be visible. The fetal heart rate should be evaluated for any signs of arrhythmia.

  • The lungs should be seen flanking the heart bilaterally, and they should appear echogenic and homogeneous, in what is described as “liver-like.” Further moving caudally in the fetus, the abdominal organs should be appreciated.
  • The stomach is seen on the left side as an anechoic cystic structure below the diaphragm.
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Bilaterally, the kidneys should present symmetrically, and the bladder should be seen in the inferior abdomen as a small hypoechoic cystic structure. From the anterior abdominal wall, the insertion of the umbilical cord should be evaluated for any sign of extrusion of intrabdominal organs.

Finally, the long bones and the spine should be followed and assessed for symmetry. The spine should be symmetric, hyperechoic, and should taper to an intact posterior skin edge. The position, movement, and tone of the extremities should also be examined. A general evaluation of the cervix is wise. First, by visual inspection, the sonographer should determine if the cervix is open or closed.

If open, the distance from the inner wall to the inner wall should be measured. Subsequently, due to the morbidity associated with cervical insufficiency, the length from the outer to the inner cervical os should also be measured. The placenta can be identified by tracing the endometrium until an isoechoic structure with increased vascularity on color Doppler.

  • The location of the placenta should be described as anterior or posterior.
  • The location of the placenta should be described as anterior or posterior.
  • The presence of placenta previa should be excluded by measuring the distance from the caudal edge of the placenta to the inner cervical os.
  • A measurement of less than 3 cm is concerning for placenta previa and should be further evaluated.

The placenta should be further inspected for masses or retroplacental hemorrhage, which will appear as heterogenous or anechoic areas, respectively. Its size in both longitudinal and transverse axes should be determined. Any abnormal finding should be further studied by applying both Color Doppler and Power Doppler modes.

  • From the placenta, the point of insertion of the umbilical cord should be traced and classified as central, eccentric, marginal, or velamentous.
  • After applying color Doppler mode to the umbilical cord, both venous and arterial flow pulsations should be distinguished.
  • Ideally, spectral doppler should be seen in the free cord, but this can be technically challenging at times.

In these cases, consistency should be preferred over accuracy, and it should be measured at a site where it can be reliably reproduced. Once a continuous wave Doppler is applied, an umbilical artery waveform following a “sawtooth” pattern should be easily discerned from the venous flow.

A resistive index can be calculated by applying the formula as follows: resistive index (RI) (Pourcelot index) = (peak systolic velocity – end-diastolic velocity) / peak systolic velocity Doppler indices are known to decline with the progression of the gestational age, given that diastolic flow increases gradually.

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If the umbilical artery resistive index is abnormal, further investigation is warranted. Finally, the amniotic fluid level should be measured by both amniotic fluid index (AFI) and deepest vertical pocket (DVP) methods if possible. To assess AFI, using the linea nigra and mediolateral lines as the axial and horizontal axis, the sonographer must divide the uterus into four different quadrants.

  • The deepest pocket identified in each quadrant devoid of both fetal parts and the umbilical cord is measured vertically.
  • The dimensions in centimeters of these measurements are added together to calculate the AFI.
  • Normal AFI is between 5 to 25 cm.
  • An AFI of less than 5 cm is considered oligohydramnios.

To determine DVP, the deepest pocket of fluid devoid of fetal parts and the umbilical cord is identified and measured vertically. A value of less than 2 cm is concerning for oligohydramnios, while more than 8 cm indicates polyhydramnios. As stated before, abnormal findings required further specialized sonographic examination and prompt consultation with an obstetrician.
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What type of ultrasound is done for pregnancy?

A fetal ultrasound (sonogram) is an imaging technique that uses sound waves to produce images of a fetus in the uterus. Fetal ultrasound images can help your health care provider evaluate your baby’s growth and development and monitor your pregnancy.
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Which scan is done in 9th month of pregnancy?

What is a morphology scan? – A morphology (body part) scan is a routine antenatal test usually done at 18 to 20 weeks of pregnancy. It is an ultrasound that checks your baby’s size and body organs. Your doctor is likely to recommend you have this test, but the decision to do so is yours.
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Which ultrasound is done in 8th month of pregnancy?

This is ultrasound after 28 weeks, commonly much later. It may also be referred to as a growth scan or late Pregnancy Ultrasound.
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Which scan is done in 6th month of pregnancy?

This detailed ultrasound scan, sometimes called the mid-pregnancy or anomaly scan, is usually carried out when you’re between 18 and 21 weeks pregnant. The 20-week screening scan is offered to everybody, but you do not have to have it if you do not want to. How Many Times Ultrasound Is Done In Pregnancy A pregnancy ultrasound scan The scan is a medical examination. You’ll be asked to give your permission for it to be carried out. Make sure you understand what’s going to happen, and feel free to ask any questions.
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