All about your pregnancy ultrasound
A foetal ultrasound (sonogram) is an imaging technique that uses sound waves to produce images of a foetus in the uterus. Foetal ultrasound images can help your health-care provider evaluate your baby’s growth and development and monitor your pregnancy. In some cases, foetal ultrasound is used to evaluate possible problems or help confirm a diagnosis.
Here’s all you need to know about ultrasounds from the Mayo Clinic.
1. The first foetal ultrasound is usually done during the first trimester to confirm the pregnancy and estimate how long you’ve been pregnant. If your pregnancy remains uncomplicated, the next ultrasound is typically offered during the second trimester, when anatomic details are visible.
2. There are two main types of foetal ultrasound exams. With the transvaginal ultrasound a wand-like device called a transducer is placed in your vagina to send out sound waves and gather the reflections. Transvaginal ultrasounds are used most often during early pregnancy. A transabdominal foetal ultrasound is done by moving a transducer over your abdomen.
3. The first trimester ultrasound examination is done to evaluate the presence, size, and location of the pregnancy, determine the number of foetuses, and estimate how long you’ve been pregnant (gestational age).
4. In the second or third trimester a standard ultrasound is done to evaluate several features of the pregnancy, including foetal anatomy. This exam is typically done between weeks 18 and 20 of pregnancy. However, the timing of this ultrasound might be altered for reasons such as obesity, which could limit visualisation of the foetus. During the second and third trimesters, limited ultrasound evaluation might be needed when a specific question requires investigation.
5. Your health-care provider might also use foetal ultrasounds to:
a. Confirm the pregnancy’s location. Some foetuses develop outside of the uterus, in the Fallopian tube.
b. Evaluate your baby’s growth. Your health care provider can use ultrasound to determine whether your baby is growing at a normal rate. Ultrasound can be used to monitor your baby’s movement, breathing and heart rate.
c. Study the placenta and amniotic fluid levels. The placenta provides your baby with vital nutrients and oxygen-rich blood. Too much or too little amniotic fluid — the fluid that surrounds the baby in the uterus during pregnancy — or complications with the placenta need special attention.
d. Identify birth defects.
e. Investigate complications. If you’re bleeding or having other complications, an ultrasound might help your health-care provider determine the cause.
f. Determine foetal position before delivery. Ultrasound imaging can confirm the baby’s presentation so that your health-care provider can discuss options for delivery.
What you can expect during the procedure
During a transabdominal foetal ultrasound, you’ll recline on an exam table and expose your abdomen. Your health-care provider or technician will apply a special gel to your abdomen. This will improve the conduction of sound waves and eliminate air between your skin and the transducer.
Your technician will move or scan the transducer back and forth over your abdomen. The sound waves reflected off your bones and other tissues will be converted into images on a monitor.
Your health-care provider or technician will measure your baby’s anatomy. He or she might print or store certain images to document important structures. You’ll likely be given copies of some of the images.
Depending on your baby’s position and stage of development, you might be able to make out a face, hands and fingers, or arms and legs. Don’t worry if you can’t “see” your baby. Ultrasound images can be hard for an untrained observer to decipher. Ask your health-care provider or technician to explain what’s on the screen.
Results
Typically, a foetal ultrasound offers reassurance that a baby is growing and developing normally. If your health-care provider wants more details about your baby’s health, he or she might recommend additional tests.
