- transvaginal ultrasound, also known as TVUS
- first trimester ultrasound
- obstetrical ultrasound
- pelvic ultrasonography in pregnancy
- obstetric sonogram
- obstetric ultrasonography
An ultrasound works something like an x-ray in that it takes pictures of the insides of the body, but it uses sound waves rather than radiation.
Who is a candidate for the test?
An ultrasound is used in women who are pregnant, or who might be pregnant. An ultrasound might be done more than once during a pregnancy, depending on the health of the baby or mother.
The many reasons that a healthcare professional might use an ultrasound in pregnancy include:
- confirm the expected date of a baby's birth
- demonstrate the reality of the pregnancy, and the features of the baby, to the expectant mother
- look for size or placement problems with the placenta
- evaluate causes of vaginal bleeding, such as a blighted ovum, which is a fertilized egg that has stopped growing
- rule out ectopic pregnancy, a condition in which the fertilized egg grows outside of the uterus
- check for intrauterine growth retardation (restriction), which occurs when the baby grows too slowly
- evaluate the volume of amniotic fluid
- assess enlarged ovaries
- diagnose multiple pregnancies, such as twins or triplets
- rule out molar pregnancy, a situation in which the fetus itself becomes a tumor
- check for abnormalities of the baby, including spina bifida, where the spine fails to close during development, or cleft palate, which is abnormal closure of the lip and roof of the mouth
- determine if the baby is alive and healthy, with good movement, heart function, and placement in the uterus
An ultrasound is used during
amniocentesis to determine the baby's position in the womb. In this procedure, a needle is placed through the abdomen to withdraw a sample of the fluid around the baby.
It is also used during
chorionic villus biopsy. With this test, the doctor takes a sample of the membrane around the baby and womb.
How is the test performed?
An ultrasound is something like the sonar used in ships at sea or by bats. As sound waves bounce off objects or organs, they can show location, size, and shape of the organ.
The equipment consists of:
- a transducer, which is a small hand-held device that looks like a microphone
- a viewing screen similar to a television or computer monitor
Liquid jelly is used on the transducer to help transmit the sound waves. The transducer both sends the sound waves and records the echoes. A computer helps translate the echoes into images. These pictures can be recorded both as video and as still images.
For the test, the woman must lie on her back or side. The lower abdomen is exposed. The transducer is moved across the outside of the abdomen. The ultrasound should take about 20 minutes to complete.
During the first three months, a probe called an endotransducer may be used instead. This probe is placed in the vagina. It can provide better images than the abdominal method in the early stages of pregnancy.
The healthcare professional may also use a Doppler ultrasound. This special type of ultrasound measures blood flow in the blood vessels and checks movement in organs. One function of a Doppler ultrasound is to check the movement of the baby's heart valves.
What is involved in preparation for the test?
The woman should wear loose-fitting, two-piece clothes. If done early in the pregnancy, the woman may need to have a full bladder. This can help with getting a clearer picture from the sound waves. A full bladder is not usually needed in the later stages of pregnancy.
What do the test results mean?
A pregnancy ultrasound can show if the baby is growing in a healthy manner with no visible problems. It shows that the baby is in a healthy position. The examiner can also tell if mother has a healthy-appearing placenta with high enough amniotic fluid levels.
Healthy ultrasound results do not guarantee a perfect baby or an uncomplicated birth, but it can usually give the healthcare professional a good sense of how a woman's pregnancy is progressing.
Abnormal results vary. A woman should discuss the results and any recommended treatments with her healthcare professional.