Why Have One?
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 Obstetricians and Gynecologists, ultrasounds are usually prescribed for the following reasons:
- To establish the baby's age: Early in pregnancy, 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 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. An anatomy scan is usually done at 18 to 22 weeks.
- To determine the position and size of the baby: Toward the end of pregnancy, 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 chorionic villus sampling or amniocentesis, or to obtain a blood sample from the umbilical cord: 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.