Fetal ultrasound

A fetal ultrasound, or sonogram, is an imaging technique that uses high-frequency sound waves to produce images of a baby in the uterus.

Fetal ultrasound images can help your health care provider evaluate your baby's growth and development and determine how your pregnancy is progressing. A fetal ultrasound might also give you the chance to study your baby's profile months before delivery. In some cases, fetal ultrasound is used to evaluate possible problems or confirm a diagnosis.

Fetal ultrasound is often done during the first trimester to confirm and date the pregnancy and again during the second trimester — between 18 and 20 weeks — when anatomic details are visible. If your baby's health needs to be monitored more closely, ultrasounds might be repeated throughout the pregnancy.

Why it's done Risks How you prepare What you can expect Results

A fetal ultrasound can be done at any point during pregnancy. Your health care provider might use a fetal ultrasound to:

  • Confirm the pregnancy and its location. Some embryos develop in the fallopian tube instead of in the uterus. A fetal ultrasound can help your health care provider detect a tubal (ectopic) pregnancy.
  • Determine your baby's gestational age. Knowing the baby's age can help your health care provider determine your due date and track various milestones throughout your pregnancy.
  • Confirm the number of babies. If your health care provider suspects a multiple pregnancy, an ultrasound might be done to confirm the number of babies.
  • Evaluate your baby's growth. Your health care provider can use ultrasound to determine whether your baby is growing at a normal rate. Ultrasound can be used to monitor your baby's movement, breathing and heart rate as well.
  • Study the placenta and amniotic fluid levels. The placenta provides your baby with vital nutrients and oxygen-rich blood. Too much or too little amniotic fluid — the fluid that surrounds the baby in the uterus during pregnancy — or complications with the placenta need special attention.
  • Identify birth defects. An ultrasound can help your health care provider detect various birth defects.
  • Investigate signs or symptoms. If you're bleeding or having other complications, an ultrasound might help your health care provider determine the cause.
  • Perform other prenatal tests. Your health care provider might use ultrasound to guide needle placement during certain prenatal tests, such as amniocentesis or chorionic villus sampling.
  • Determine fetal position before delivery. A C-section might be needed if the baby is in an abnormal position.

If your health care provider doesn't suggest a fetal ultrasound but you'd like the reassurance the exam can provide, share your wishes as you work together to determine what's best for you and your baby.

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