Ultrasound Scan During Pregnancy

One of the most helpful of medical technologies, ultrasound is now a routine part of prenatal care. Ultrasound scans are used to check your baby's general well-being and position, and guide doctors when they're carrying out any special tests and operations. You'll be given two scans-the first at around 12-13 weeks, to confirm dates and check whether you're expecting more than one baby. If your first visit to your midwife or doctor is after 13 weeks, you'll have a scan then. Between 18 and 20 weeks you'll have another scan to make sure your baby is growing well and there are no abnormalities. If all looks fine, you won't have any more scans.

How It Works

The process is based on a sonar device that reveals objects in fluid, which was first used by the US Navy to detect submarines during World War II. A crystal, inside a device called a transducer, converts an electrical current into high-frequency sound waves, which the human ear can't detect. The sound waves form a beam that penetrates the abdomen as the transducer is moved back and forth. The beam reflects off material in its path, and the transducer records these echoes. The echoes are converted into electrical signals, which produce an image that can be displayed on a screen. The beam can only penetrate fluids and soft tissue such as the amniotic sac, kidneys, and liver. It cannot pass through bone, or register gas. An ultrasound scan is increasingly used to assess the threat of miscarriage, make sure you're not having an ectopic pregnancy, and assist in infertility treatments, such as IVF, and fetal surgery.

Your Scan

Your ultrasound scan can be a thrilling moment for you and your partner-a chance to see your baby for the very first time. Scanning equipment has been improved and refined over the years, and the technique is not intrusive.

You should be able to hear your baby's heartbeat, and to see the gentle movement of her hands and feet, waving and kicking, as she floats in the amniotic fluid. Ask the ultrasound operator to explain the image on the screen to you, since some details may be difficult to make out. Some clinics will offer you a print of the image of your baby as a memento to cherish, although they may charge you for this.

Is It Safe?

There are no known risks to your baby from an ultrasound scan. There have been some worries about long-term effects, such as hearing impairment caused by the impact of sound waves, but recent research suggests that ultrasound is not harmful to mother or baby. The waves are of a very low intensity, and so it's safe for the scan to be performed repeatedly.