If you're pregnant, chances are you'll have an ultrasound at some point. Read the answers to these commonly asked questions to learn what ultrasounds are, why they're necessary, and what they feel like.
What's an ultrasound?
Ultrasounds help doctors see internal fetal and maternal structures. The ultrasound probe, or transducer, goes either on the mother's abdomen or, less frequently, inside her vagina. The transducer transmits high-frequency sound waves that echo back and are transformed into a picture on a video screen. This picture shows the fetus inside the womb. Often, parents will be given a printout of the ultrasound to keep.
At six weeks' gestation, it's possible to see the baby's heartbeat. For many expectant parents, it's an added bonus that an ultrasound given after 20 weeks can sometimes identify the sex of the baby. However, in some cases it's not possible to see the baby's genitalia and parents are kept guessing.
Why an ultrasound?
Ultrasounds have many applications in pregnancy, and up to 60 percent of expectant mothers receive at least one scan. According to the American College of Obstetrics and Gynecology, ultrasounds are usually prescribed for the following reasons:
- To establish the baby's age. Ultrasound helps accurately date a pregnancy, preventing unnecessary interventions. About 30 percent of pregnancies have dating errors. For dating purposes, an ultrasound scan should be performed prior to 20 weeks; it's typically scheduled between 12 and 16 weeks.
- To see the baby's heartbeat. In late pregnancy, Doppler ultrasound enables a technician to measure circulation in the placenta and umbilical cord. This technique, called velocimetry, evaluates fetal well-being in pregnancies that are at risk because of growth retardation in the baby or high blood pressure in the mother.
- To identify fetal abnormalities. Because it allows the physician to see the baby's developing body in great detail, an ultrasound is key in the detection of fetal abnormalities.
- To determine the position and size of the baby. With an ultrasound, a doctor can see a baby in breech position and determine if the baby is too big to fit through the mother's pelvic cavity.
- To detect multiple pregnancies. Scans help confirm multiple pregnancies and assess the babies' growth and health.
- To perform the genetic test chorionic villous sampling, or to obtain a blood sample from the baby. An ultrasound helps safeguard certain genetic-testing procedures by allowing the doctor to ascertain the safest place to insert a catheter or needle.
- To assess pregnancy complications such as bleeding or pain. Ultrasound helps the physician see the source of the bleeding and identify possible complications such as placenta previa.
