Your first prenatal test

Most women are excited for their first ultrasound. It offers a sneak peak of the unborn baby and might offer hints at its sex. Your doctor will let you know how often you need an ultrasound. Most women will have one or two ultrasounds during pregnancy. Here's what to expect for this prenatal test.
What is an ultrasound?
An ultrasound uses high-frequency sound waves to create a picture of your unborn baby. It also shows images of your uterus, amniotic sac, placenta and ovaries.
In this procedure, a small device called a transducer sends sound waves into the body. The waves reflect off internal structures, including your baby. Then the transducer receives the sound waves and sends a picture to a screen.
The images appear on the screen during the exam. Pictures can be printed or the whole procedure can be recorded on video. Your doctor can usually discuss results of an ultrasound with you soon after the exam is over.
Why is ultrasound used in pregnancy?
Ultrasound is used to:
Check on your baby's health status, including position, movement, breathing, growth and heart rate
Make sure the placenta is healthy and attached normally
See the number of fetuses
Calculate the expected due date
Detect some birth defects
See how much amniotic fluid is in the uterus
Ultrasound can also be used to diagnose a possible miscarriage or ectopic pregnancy, or to determine the cause of vaginal bleeding. Sometimes it can give you a hint as to the sex of the baby. This is not always accurate, though.
How do I prepare for an ultrasound?
You'll need to have a full bladder, which can be uncomfortable, especially during pregnancy. But a full bladder pushes the uterus up for better viewing. You may be asked to drink up to six glasses of water in the two hours before the exam. You can't urinate until the ultrasound is over. Wear clothes that make it easy to expose your abdomen. The exam usually takes 15 to 20 minutes.
What are the different types of ultrasounds?
There are two main types of ultrasounds: abdominal and vaginal.
Abdominal ultrasound. You'll lay on a table with your abdomen exposed. Then the ultrasound technician puts a gel on your abdomen. The gel improves how the transducer works on your skin. The transducer is gently placed on your abdomen and moved over your stomach and pelvis. There are two more detailed types of abdominal ultrasounds:
Doppler. Higher-intensity sound waves are used to study the movement of blood and listen to the baby's heartbeat.
Three- and four-dimensional (3-D and 4-D). The 3-D ultrasound takes thousands of images at once, making the image look more realistic. A 4-D ultrasound shows movement as well as still shots.
Vaginal ultrasound. The vaginal ultrasound can take a closer look at the organs and fetus. It is used more often in early pregnancy.
For this procedure, you will change into a hospital gown, lie down and put your feet into stirrups, like you are preparing for a pelvic exam. A protective sheath is placed over the transducer and then it's inserted into the vagina. The ultrasound procedure is painless. You may feel mild discomfort from the pressure of the transducer.
Is ultrasound safe?
There is no evidence that ultrasounds are harmful to mom or baby. They have been done for many years without problem. But the American College of Obstetricians and Gynecologists and the American Institute of Ultrasound in Medicine discourage the use of ultrasounds for nonmedical purposes. Using an ultrasound to detect the sex of the baby or to take a keepsake photograph should be done only if the ultrasound is needed for medical reasons - and only by certified medical personnel. Even though there are no known risks linked to ultrasounds now, it is possible that some will be found in the future. Radiation is not used for ultrasound.