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Ultrasound Exam
Ultrasound (US) imaging is a method of obtaining images of internal organs in the body by sending high-frequency sound waves into the body. The image itself is the sound wave echoes of the ultrasound. As the sound waves bounce against objects, its echoing waves can be used to identify how far away the object is, how large it is, its shape and its internal consistency, be it fluid, solid or mixed. These sound waves are instantly measured and displayed on a computer as a video or still picture. A benefit of ultrasound is that no ionizing radiation is involved, unlike conventional x-rays. In pregnancy, obstetric ultrasound uses sound waves to visualize and determine the condition of a pregnant woman and her embryo or fetus. Almost all women are offered at least one ultrasound exam during their pregnancy, and, in higher risk cases, women may be given ultrasounds throughout their term. In the first trimester, ultrasound is often used to confirm and date a pregnancy (it is a very accurate method of determining fetal age early in gestation). Many health providers advise an ultrasound exam between weeks 17 and 19 for evaluating fetal development and excluding abnormalities (this is often a more detailed exam, called an "anatomy scan," in which the baby is carefully measured for possible abnormalities). In the third trimester, ultrasound may be used to assess the health, position, and size of the baby and the placenta. It is sometimes, though not always, possible to determine the gender of the baby from ultrasound after about week 16. Risks and Benefits of Ultrasound Ultrasound is safe for you and your baby because it does not use x-rays to produce an image. Using sound waves so high they can't be heard by the human ear, ultrasound allows visualization and "examination" of the fetus without X-rays. Studies show that low-risk women who have routine ultrasound exams are no more likely to have healthy babies than low-risk women how don't have the test. The only potential risk is the chance that ultrasound may not detect all birth defects, and occasionally give a false positive result, where the patient is told incorrectly that her baby may have a birth defect. Frequent follow-up exams can ensure that false positive results are kept to a minimum. Often an exciting experience for parents-to-be, an ultrasound exam is painless and non-invasive. High-frequency sound waves (which cannot be heard by humans) are reflected off of the baby's body, creating an image,or sonogram, of the baby that can be viewed on a small screen. To conduct the exam, the doctor or technician applies some oil or gel on your exposed abdomen, then moves a transducer across it. The transducer directs sound waves toward your uterus and the fetus inside the uterus. (Early in pregnancy, when the fetus is very small, the exam may be conducted with a transducer in the shape of a wand, which is inserted vaginally.) Ultrasound involves no radiation or X-rays, and is considered harmless for both mother and baby. There are several indications for ultrasound in a pregnant woman including:
Preparing For the Ultrasound Your doctor will explain that you should wear loose fitting clothes for the examination. Only the lower abdominal area needs to be exposed during this procedure, so wear something that can be easily removed. You may be required to have a full bladder because this will push the air-filled bowel out of the way and allow an unobstructed view of the uterus, embryo or fetus. You may be instructed to drink up to six glasses of water and avoid urinating during the two hours before the procedure. If you are having the ultrasound later on in your pregnancy, a full bladder is generally not required. The Procedure A level 1 ultrasound is usually done to date a pregnancy and is performed before 12 weeks. A more detailed (level 2) ultrasound is used for more sophisticated diagnostic procedures and is normally done between week 18 and 22. A benefit of ultrasound is that it is a painless procedure. The only discomfort that you may feel would be when the radiologist guides a hand-held device (called a transducer) over your abdomen. Occasionally, a device may need to be inserted into your vagina but again pain is not common, only discomfort. At times, the ultrasound device may have to be pressed more firmly to get closer to the embryo or fetus to better visualize them. The exam typically takes about 20 minutes. During the exam you will lie on your back. A film gel is applied to the abdomen to improve the conduction of sound. A transducer is then moved slowly over the abdomen or inserted into the vagina, and the instruments record echoes of sound waves as they bounce off parts of the baby and translates them into pictures. A medical radiologist will then analyze the images that were produced during the ultrasound and send a signed report with his or her interpretation to the patient's personal physician. You may be able to differentiate the beating heart, the curve of the spine, or the head, arms and legs. Getting the Results The findings of an ultrasound exam are available immediately. It's a good idea for your partner to come with you -- during the exam, you'll learn important news about your baby's well-being. The accuracy of the exam's findings depends largely on the skill of the practitioner or the ultrasound technician who is interpreting the data and images, and, to some extent, on the position of the baby during the exam. An experienced user of ultrasound equipment will usually be able to give you an accurate assessment of what's going on inside your uterus. In some cases, you may receive a "photo" of your baby, a videotape, or a three-dimensional image that you can show to your friends and family. If you don't want to know your baby's sex in advance, be sure to let the doctor or technician know as sometimes the genital organs are distinguishable and the sex can be surmised with ultrasound.
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