Ultrasound: A Womb With a View

Last Editorial Review: 1/30/2005

Ultrasound Testing: A Womb with a View

WebMD Feature

Carla Laszlo and her husband Robert recently went for a 20th-week ultrasound, and seeing the baby come to life on the computer screen before them was an experience like no other. The Southwick, Mass., couple even brought home photographs and a video, just in case they need another fix before meeting the genuine article in December.

"To see your baby for the first time and count fingers and toes is spiritual," says Laszlo. "I was absolutely mesmerized. Aside from desperately wanting to see this little creature inside of me was the anxiety that everything would be forming perfectly and that the baby would be healthy. The news couldn't have been better. To celebrate, we bought a crib!"

More than half of pregnant women have at least one ultrasound, also known as a sonogram, sometime during their pregnancy. The test, which works by bouncing harmless sound waves off the fetus to create an image onto a computer screen, can help doctors and midwives monitor the development of your fetus and help assess various conditions, including some birth defects.

Ultrasounds are also typically a welcomed rite of passage for expectant parents. Not only can they give peace of mind (or, on the flip side, advance warning of a condition that might require other decisions and planning), but the pictures are often parents' first tangible peek at the miracle growing inside. "It was a real bonding experience," says Janet Kalbhen, a Chicago free-lance Web consultant.

"Even though you know intellectually that there's a child growing inside you, when you see it on the screen and you can see a heartbeat and see it moving, you just feel more connected. It felt like a baby, instead of a fetus, to me at that point," says Kalbhen, who had several ultrasounds before her baby was born two years ago.

The Powers of a Jelly Belly

If you're offered a sonogram, chances are that your doctor or midwife is trying to assess something in particular. The American College of Obstetricians and Gynecologists (ACOG) and the National Institutes of Health (NIH) discourage routine ultrasounds, but instead suggest that ultrasound screening be done for specific indications.

The most common reasons for an ultrasound include verifying a due date and number of fetuses; measuring the baby's growth, movement, position, heart rate and breathing; locating the placenta; diagnosing most structural defects, such as congenital heart diseases or cleft lip; assessing the root of complications, such as bleeding; or guiding doctors through diagnostic tests, such as amniocentesis or chorionic villi sampling (CVS).

The procedure can be done two ways. In the first trimester, a transvaginal ultrasound is usually most informative and takes only a few minutes. A flexible probe called a transducer is inserted into the vagina, which allows a close-range view of the gestational sac, fallopian tubes and fetus. The standard second-trimester scan takes about 20 minutes and is done by moving the transducer gently over the abdomen, which is covered with a special jelly that conducts sound waves.

Doctors used to tell patients not to ask the ultrasound technician questions about what's projected onto the screen and to wait instead for the radiologist's report and an explanation from their health-care provider. But Dr. John Larsen, a professor of obstetrics, gynecology and genetics at The George Washington University, says such etiquette is unrealistic.

"The current milieu, for better or worse, is to talk about what's going on while it's happening," says Dr. Larsen. "The technician can say 'There's the head; there's the heart; there's the limbs; these are the testicles,' and on you go."

If there's something wrong, waiting is often impractical because everyone's attention is on the screen. "It's right in your face," Dr. Larsen says. "Patients feel a tremendous sense of discomfort if suddenly the technician isn't talking to them."

Despite the ACOG and NIH recommendation that sonograms be done only for specific purposes, many doctors routinely order an ultrasound between 18 and 20 weeks to head off problems that otherwise might not be apparent.

"When a pregnant woman goes to the doctor, why should that doctor only look at the mother?" asks Dr. Ilan Timor, director of New York University Medical Center's obstetrical and gynecological ultrasound unit. "We have the tools to look at the fetus to anticipate things, so why shouldn't we?" Pregnant women in other countries, such as Germany, Sweden and Denmark, are typically offered at least two.

The crux of the controversy centers on the cost-effectiveness of offering these scans. The results don't necessarily reduce complications or defects, even though many parents and doctors say they'd still prefer knowing what they're in for. Moreover, false positive and false negatives do occur, and one large study done in the 1980s showed that many ultrasounds are misread.

Those results also became fodder for insurance companies that want to keep down the cost of reimbursements. According to the National Center for Health Statistics, about 2.5 billion ultrasounds were done in 1997, representing 64% of all pregnancies. Hospitals typically charge $240 for an ultrasound, but reimbursements can be as low as $38, with health plans usually covering one or two ultrasounds.

But experts say accuracy rates will be higher in the hands of experienced doctors or imaging facilities with high-quality machines. The American Institute of Ultrasound in Medicine and the American College of Radiology give accreditation based on factors such as the condition of the machine and the sonographer's experience and education. In fact, many insurance companies will only cover accredited doctors and facilities.

How do you know? Ask if the unit is accredited, and find out if the picture you're getting will provide as much information as possible about your baby's well-being, says Dr. Larsen. "If the doctor says, 'No, this is a very brief scan to see if the baby is head first or feet first,' then ask if it's possible to get a more detailed view to see all the organs. He'll know what's going on then and (he will) send you to Dr. X who does this on a regular basis."

Adds Dr. Timor: "The typical office ultrasound can be done for very simple things, such as detecting a heartbeat or locating the placenta or fetus position, but malformation work-ups should be done in an expert place. That's a very serious matter."

It's also important to understand what an ultrasound can -- and can't -- tell you.

"Healthy and physically normal are two different things," says Dr. Fay Redwine, director of perinatal services for St. Mary's Hospital and two others in Richmond, Va. "An ultrasound is a physical exam, not a functional one. For instance, an ultrasound can't detect all Down syndrome cases, only about half, and babies with genetic metabolic problems or cerebral palsy have normal ultrasounds." If Down syndrome is suspected, for instance, a follow-up diagnostic test, such as amniocentesis, would be a better predictor.

Nor should you even assume that an ultrasound will accurately predict the gender. For one thing, you need to be at least 15 weeks pregnant for genitals to show up on an ultrasound, and then the clarity still can be foiled by the fetus' position. Kalbhen says an ultrasound at five months indicated she was having a girl, yet two weeks before delivery another sonogram showed that "Sarah" had to be renamed "Daniel."

New Dimensions

After Richele and Morgan Rapp had seen two ultrasounds of their baby they were excited -- that is, after they got some help deciphering which blurry blob was the head, which squiggly lines were the arms and which were the legs. But when their doctor invested in a new three-dimensional machine, the Aurora, Colo., couple were blown away by the detail.

"It was breathtaking," says Richele. "It wasn't a struggle to try and make out what you were looking at. This looked like a baby."

Not only could they see all the details of the face -- cheeks, nose, eye sockets -- and watch its fingers and toes move, but they could make out skin tissues of the legs and arms, all four chambers of its heart, and even see the blood and oxygen pumping through its body. "The picture was so vivid, like you were sitting with a video camera taping it," says Morgan.

These high-tech machines aren't available in most facilities yet, mostly because they cost about six times as much as a standard two-dimensional machine. Nor can they provide much more information to sonographers, who are already trained to see 3-D details in the standard 2-D image.

But for about 5% of cases, the new 3-D machines may have advantages over the traditional machines, says Dr. Timor. For instance, certain surface abnormalities, such as cleft lip, will be more distinguishable to parents and cosmetic surgeons, so that parents can be better counseled on the extent of the condition and corrective measures. They might also make it easier for doctors to localize problems in fetal brain development.

Don't count on those 3-D pictures for your baby books just yet. Until insurance companies start more realistic reimbursements, says Dr. Timor, even facilities that can afford to buy these machines won't be able to use them on most patients because they'll lose too much money. Analyzing 3-D images is more time consuming and, in most cases right now, doesn't provide information to doctors that's significantly different than 2-D.

Another new development involving ultrasound is an experimental procedure to screen earlier for cases of Down syndrome and some other chromosomal abnormalities. The test, done between 10 and 14 weeks, combines a detailed measurement of skin at the back of the fetus' neck with levels of two pregnancy hormones.

The NIH is giving $12 million to 10 medical centers to study how effective the test is at detecting defects. "Some people say that by blending together those two measurements you can pick up as high as 90% of cases of Down syndrome and a variety of other syndromes as well," says Dr. Larsen.

The test allows earlier screening than the maternal serum alpha-fetoprotein and multiple marker screens, which are done between 15 and 18 weeks, and may even give some couples enough peace of mind to reduce the need for amniocentesis and CVS -- invasive diagnostic tests with a slight chance of miscarriage.

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