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pregnancy ultrasound Alternative Names
transvaginal ultrasound(TVUS), first trimester ultrasound, obstetrical ultrasound, pelvic ultrasonography in pregnancy, obstetric sonogram, obstetric ultrasonography
Definition
An ultrasound uses sound waves to make black-and white pictures of body structures. A hand-held device called a transducer sends high-frequency sound waves through the body. The sound waves reflect off of body structures. A computer converts the reflected waves into two-dimensional, or recently three-dimensional, pictures. An ultrasound allows a doctor to view a woman's uterus, ovaries, and fallopian tubes. It allows a developing baby to be evaluated, and lets the doctor view the placenta. The placenta is an organ that supplies the baby with oxygen and nutrients. The amniotic fluid, which surrounds a baby, can be seen.
A transvaginal ultrasound might be done during the first three months of pregnancy. For this test, the transducer is placed in the vagina. An abdominal ultrasound might be done later in pregnancy. For the abdominal ultrasound, the transducer is placed on the abdomen.
Who is a candidate for the test?
An ultrasound can be done for a woman who is 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 woman.
A doctor uses an ultrasound for many reasons. These reasons include: - confirming the expected date of a baby's birth.
- looking for size or placement problems with the placenta.
- evaluating causes of vaginal bleeding, such as a blighted ovum, which is a fertilised egg that has stopped growing.
- ruling out ectopic pregnancy, in which the fertilised egg is growing outside of the uterus.
- checking for intrauterine growth retardation, which occurs when the baby grows too slowly.
- evaluating the volume of amniotic fluid.
- assessing enlarged ovaries.
- diagnosing multiple pregnancies, such as twins or triplets.
- ruling out molar pregnancy, a situation in which the foetus itself becomes a tumour.
- checking for problems with the baby. This includes spina bifida, which is an open spine, or cleft palate, which is abnormal growth of the lip and roof of the mouth.
- determining 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 within the uterus. In this procedure, a needle is placed through the abdomen to withdraw a sample of the fluid surrounding the baby. It is also used during chorionic villus biopsy. This test involves a piece of the membrane that surrounds the baby and uterus.
How is the test performed?
During the first three months, the transducer, or hand-held device, is covered with a liquid jelly and placed within the vagina. After the second trimester, the transducer can be placed on the abdomen. The abdomen is covered with a liquid jelly to help send the signal.
The doctor may also use a Doppler ultrasound. This special type of ultrasound measures blood flow in the blood vessels. It checks movement in organs. For example, the doctor can use a Doppler ultrasound to evaluate the movement of heart valves.
What is involved in preparation for the test?
For an obstetric ultrasound, a woman may need to have a full bladder. She can ask her doctor how to prepare for her ultrasound.
What do the test results mean?
A normal pregnancy ultrasound indicates that the baby is growing normally with no visible problems. It shows that the baby is in a normal position. It also shows that the mother has a healthy-appearing placenta with adequate amniotic fluid levels.
Normal ultrasound results do not guarantee a 'perfect' baby or an uncomplicated birth. The test provides helpful information about how a pregnancy is progressing.
Abnormal results vary. A woman should discuss the results and potential treatments with her doctor.
Author: Eva Martin, MD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 6/06/2005
Contributors
Potential conflict of interest information for reviewers available on request |
