Pregnancy Ultrasound

Importance of Pregnancy Ultrasound : How, When and Why?

  • Pregnancy ultrasound uses sound waves and a computer screen to show a picture of a baby in the womb. 
  • Ultrasound can help radiologists / sonologist to see how the baby is developing. 
  • Radiologists may also use ultrasound to see if other tests are needed to monitor your fetus’s health.
  • There are many types of ultrasound and they are safe for you and your child when performed by a trained healthcare provider.

What is a pregnancy ultrasound?

Ultrasound is a type of imaging technique that uses sound waves to create fetus images in the womb. During pregnancy, a transducer (or stick) is placed into the vagina or upper abdomen. It emits sound waves that bounce off the baby’s tissues, fluids, and bones. The transducer then picks up these echoes and transforms them into the image of the baby that can be seen on the screen.

In early pregnancy, ultrasound scans are used to confirm the fetal heartbeat and the location of the pregnancy. Later, ultrasounds evaluate fetal development and placenta, as well as the baby’s health and general anatomy.

Towards the end of pregnancy, an ultrasound can be helpful in checking the length of the cervix, if there is any doubt about preterm labor, as well as checking that your baby is head-to-head before delivery or is in the lower position.

Why is an ultrasound done in a pregnancy?

A prenatal ultrasound is done for :

  • To confirm the expected delivery date.
  • Find out the pregnancy outside the uterus.
  • See if there can be more than one fetus.
  • See if the fetus is growing at a normal rate.
  • Record fetal heartbeat or respiratory movements.
  • Check the volume of amniotic fluid in the uterus.
  • Check the status of the placenta (which can sometimes block the baby from the uterus) in late pregnancy.
  • Guide doctors through other tests, such as amniocentesis.
  • Detect structural defects that may indicate Down syndrome, spina bifida, or anesthesia.
  • Also detects congenital heart defects, cleft lip or palate, and gastrointestinal or kidney problems.


How many types of ultrasound are done during the pregnancy?

  1. Transvaginal ultrasound: When the fetus is very tiny during early pregnancy, a transvaginal ultrasound, or endovaginal ultrasound is recommended to take a better picture of the fetus. The procedure involves inserting an ultrasound probe 2 to 3 inches into the vagina, while the transducer is held outside the pelvis. This is usually done to check for vaginal bleeding, to monitor the baby’s heartbeat, to examine the placenta, to confirm an early pregnancy or a suspected miscarriage.
  2. Standard transabdominal ultrasound: transabdominal ultrasound is a standard ultrasound that evaluates a fetus at 8 weeks’ gestation. With this process, a transducer attaches to the monitor while it passes through the stomach. The transducer produces sound waves, echoes, and images on the monitor. 
  3. Doppler ultrasound: Doppler ultrasound uses sound waves or echoes to check blood flow in vessels. Doppler ultrasound during pregnancy helps assess blood circulation in the fetus, uterus, and placenta.
  4. 3D ultrasound: A 3D ultrasound is a transabdominal ultrasound that takes two-dimensional images of a fetus which is then computer translated into three-dimensional images that are presented as real-life photographs. Although 3-D images look very attractive, studies have shown mixed results on the performance of 3-D ultrasound.
  5. 4-D Ultrasound During Pregnancy: Unlike 2-D or 3-D images, 4-D ultrasound uses a scanner that captures the baby’s movement in addition to images. 
  6. Fetal echocardiography during pregnancy: With this technique, doctors can evaluate a baby’s heartbeat. This involves placing self-adhesive electrodes on the chest and primarily for monitoring congenital heart disease.


How many types of ultrasound are done during the whole period of pregnancy?

This is the question that comes and worries every pregnant woman. A recommended number of ultrasounds for routine prenatal care has not been recorded. And because ultrasound does not have scientific proof that it causes any problems and therefore it is safe, so it can be performed at any time during pregnancy. 

Prenatal ultrasound is usually done every trimester to assess the health of the uterus mother and fetus.

  1. Ultrasound during the first trimester of pregnancy: During the first trimester of pregnancy, an ultrasound is done to check the viability of the fetus, find the due date, check the baby’s heartbeat, number of pregnancies, and also check to bleed from the vagina usually happens when you are 6 to 8 weeks pregnant. 
  2. Ultrasound during the second trimester of pregnancy: During the second trimester of pregnancy, this ultrasound, also known as anatomy ultrasound, is used to check the development of the fetus, and birth defects or congenital disease, anatomy, and the fetus are used to evaluate for the gender. Determination of sex is prohibited in India. Between the 18–20 weeks of pregnancy, a second ultrasound is advised.
  3. Ultrasound during the third semester of pregnancy: Ultrasound in the third trimester of pregnancy is done to evaluate the fetus’s development, any abnormalities, or any changes in the fetus’s condition. It is done at 32–34 weeks of pregnancy.


When to do an ultrasound if there are Twins or Triplet Pregnancy?

According to the National Institute for Excellence in Health and Care, women who are pregnant with twins or triplets (known as multiples) are advised to have an ultrasound between 11  and 13 weeks  6 days of pregnancy. 

In addition, doctors make sure to label the fetus in cases of multiple pregnancies using ultrasound. 

Additionally, women with multiple pregnancies are advised to have a detailed scan every 4 weeks after the second trimester to check for any structural abnormalities.


Is Pregnancy Ultrasound safe?

There is a risk in all medical procedures. However, there is no evidence to show that properly performed prenatal ultrasound will harm the mother or fetus. Correctly this means that it is performed by a doctor or a trained technician, called a sonographer. Ultrasound does not use radiation, as do other procedures, such as X-rays.

Conclusion about Prenatal Ultrasound?

A prenatal/ pregnancy ultrasound is a prenatal test that involves the use of high-frequency sound waves to obtain images of the uterus of a child and mother. This is definitely an exciting time for parents but go for an ultrasound if recommended by a doctor. Even if the scan is considered safe, you should use ultrasound and avoid unnecessary scans. Locate an experienced ultrasound specialist and select procedures that provide good results while providing minimal risk.

(Disclaimer: Information provided in this piece of article is purely for educational purposes only. All results must be clinically correlated with the patient’s data to make an accurate diagnosis.) 

References :
  1. Better health channel. Department of Health and Human Services [Online]. The state government of Victoria; Pregnancy tests – ultrasound .
  2.  National Institute for Health and Care Excellence. Multiple pregnancy: twin and triplet pregnancies. [Online].
  3. A. Khalil et al. ISUOG Practice Guidelines: role of ultrasound in twin pregnancy. Ultrasound in Obstetrics & Gynecology.
  4. MedlinePlus Medical Encyclopedia: US National Library of Medicine; Ultrasound pregnancy.

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