Ultrasound

An ultrasound is a prenatal tool used by your health care provider to measure your baby's growth and evaluate the development of important organs and structures, including the head, abdomen, heart, stomach, bladder, umbilical cord and placenta. A technician uses a transducer to transmit high frequency sound waves through your skin and into your uterus where they bounce off your bones, organs and your baby. A computer then translates the sound waves into a video image that reveals your baby's shape, position and movements. Ultrasound technology has been used for over four decades and is considered safe for both you and your baby.

You will probably be asked to arrive at your ultrasound with a full bladder, which eliminates pockets of air between your uterus and bladder and will provide clearer images. The technician will apply a gel to your abdomen to improve the conductivity of the sound waves and to prevent air pockets developing between the transducer and your skin. As the sound waves bounce off your organs and your baby and are transmitted back through your abdomen, a black and white image will appear on the monitor. The image will be fuzzy and can be hard to decipher to the untrained eye, but the technician can help you understand what you are looking at. The images will be analyzed by a trained specialist and the results sent to your health care provider. Most ultrasounds take approximately 30 to 40 minutes.

An ultrasound can be performed at any time during pregnancy and there are no specific guidelines for the number of ultrasounds a woman should have during her pregnancy. A healthy woman in her 20s might not need any, whereas a woman with gestational diabetes will need regular scans to monitor the size of her baby. Most doctors and midwives will perform an initial ultrasound exam at your first prenatal appointment and you may also have what is called a Level 2 ultrasound between 15 and 22 weeks. This ultrasound uses more sophisticated and sensitive equipment and can be used to look for potential problems, as well as gain more detailed information about your baby's growth and development.

Most expecting parents look forward to an ultrasound because it gives them a first glimpse at their baby. But doctors and midwives use Level 2 ultrasound technology to gather a wealth of information about your baby and your pregnancy. They can:

• Take accurate measurements of your baby, which are used to ensure your baby is growing as he or she should and confirm your baby's gestational age and estimated due date.

• Determine whether you are carrying more than one baby, such as twins or triplets, and evaluate their growth.

• Locate your placenta.

• Evaluate your baby's heartbeat.

• Assess the amount of amniotic fluid in your uterus.

• Use it to guide them as they perform other diagnostic tests such as amniocentesis.

• Detect certain birth defects.

If an ultrasound shows a potential problem, don't panic. In most cases you will be referred to a specialist in diagnostic fetal medicine for a more detailed exam. This may be done with a three-dimensional (3D) scan which uses a computer to create a 3D image of your baby, enabling the specialist to see a cross-section of any part of the body. In most cases, the follow-up ultrasound will find that your baby is healthy; however, if a problem is confirmed, the early diagnosis will help ensure you and your baby receive the best prenatal care.

Once the ultrasound technician verifies ten fingers, ten toes, two arms and two legs, he or she may be able to tell you whether you are carrying a boy or a girl. An ultrasound performed between 20 and 22 weeks is 95 to 99 percent accurate in determining the baby's sex; any earlier and the genitals are too small to identify. Any later and your baby will be too large to see clearly between the legs. Technicians are instructed not to tell their patients the baby's sex automatically; but if you don't want to know, it's best to let the technician know right away. Try not to draw any conclusions if the technician refers to the baby as a "he" or "she"; they may call the baby one or the other as opposed to using the pronoun "it."