Imaging Multiples

A sonographers guide

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A sonogram of twins (Philips Medical Systems)

A sonogram of triplets

Septuplets in the womb

Toshiba's line of ultrasound systems, including the AplioXG (pictured here), can be used to image multiple fetuses. (Toshiba America Medical Systems Inc.)

Tips for Imaging Multiples

When imaging multiples, sonographers should keep in mind the following tips:

• Make sure you know who is who when imaging multiple births. Create a drawing so that you know where babies A, B and C are. Keeping track can become difficult. When dealing with one uterus with three gestational

sacks, it can be tricky to determine which fluid belongs to who – but it's important for a useful image.

Be meticulous and patient. Don't hurry. Plan the time in advance. Allow a triplet sonogram to be longer than a typical single-growth study.

Give a good, thorough exam. Identify if the twins are monochronic and diachronic.

Although scanning multiples isn't tremendously different than a single fetus, it does take time and skill. Be sure to tuck these tips away somewhere safe. With the trend of multiple pregnancies growing, you will be sure to come across more and more multiples.

—D.B.M.

Expand

• Are there any special imaging issues with multiple pregnancies?
• What should I be looking for when performing an ultrasound on a mother with multiple fetuses?
  
• Are there any special techniques I should know before imaging multiples?
• Are there cutting-edge technologies available for imaging multiple pregnancies?
• Is the machine I'm using the most appropriate?
  

This article will answer these questions for you and explore other issues related to multiple pregnancies.

A Burgeoning Trend

Two key factors are responsible for the increasing numbers of multiples, according to the National Center for Health Statistics: the fact that the growing popularity of fertility treatments, such as ovulation-inducing drugs and in vitro fertilization, and the increasing number of women in their late thirties are giving birth.

The National Center for Health Statistics state that about 20 percent of women undergo fertility treatments have multiple births, as opposed to approximately 1.5 percent of all women giving birth in the United States.

The epidemic of multiples in this country is so high from in vitro because "insurance companies are not covering for the cost of in vitro, therefore, patients are paying for this out of their own pocket [which is costly, sometimes up to $20,000 a cycle] and instead of having one embryo implanted they are choosing to implant three, four and even five embryos at a time to avoid another attempt at in vitro," explains William H. Clewell, MD, director of obstetric ultrasound at Phoenix Perinatal Associates and Banner Good Samaritan Medical Center in Ariz.

"The one thing that patients don't always take into consideration is the 5 percent incidence that all of the embryos can take. It's technically possible to reduce the fetuses in multiple pregnancy cases, but this is emotionally difficult and many patients choose not to go this route."

Multiple pregnancies are more common in the United States because in some countries the public health system will pay for in vitro with the stipulation that you can transfer only one embryo at a time. This approach has garnered much political discussion.

The second reason for the increase in multiple pregnancies is the fact that many women are delaying reproduction until their mid- to late-thirties.

Scientists believe that women between the ages of 35 and 39 are more likely to give birth to multiples than women in other age groups because the body begins to produce higher levels of gonadotropin hormones, which cause more eggs to mature and be released from the ovaries. The National Center for Health Statistics attributes one-third of the rise in multiple births to this age factor.

Imaging for Multiple Births

Being pregnant with more than one baby is often a happy event for many couples. However, there is a higher incidence for risks and complications with multiple pregnancies. When you image a patient who is pregnant with multiples, you must look for signs of these complications. According to Clewell, some of complications include:

• Birth defects. Multiple birth babies have about twice the risk of congenital abnormalities, including neural tube defects (such as spina bifida), gastrointestinal and heart abnormalities.
• Toxemia pregnancy. This condition is also known as pre-eclampsia, and it's a form of high blood pressure. The only cure for this is delivery.
• Amniotic fluid abnormalities are more common in multiple pregnancies, especially for twins that share a placenta.
• Twin-to-twin transfusion syndrome. This is a condition of the placenta that develops only with identical twins that share a placenta. Blood vessels connect within the placenta and divert blood from one fetus to the other. It occurs in about 15 percent of twins with a shared placenta.

A number of patients who are pregnant with twins, triplets and quadruplets come from all over the country to the maternity center at Banner Good Samaritan Medical Center. As one of the nation's leading centers for multiple births and high-risk obstetrics, it delivers more twins, triplets and quadruplets than any facility in the nation.

"When we image a patient with multiple pregnancies, we use standard 2-D imaging," says Clewell. "In fact, we don't use 4-D imaging for multiple pregnancies. We don't find it helpful in quads. People use it for nice pictures of babies' faces and, to do this, there needs to be spaces around them. There isn't enough amniotic fluid between the babies in the case of multiples."

Two-dimensional imaging keeps on improving all the time and the life expectancy of the ultrasound machines is about three to five years. "All you need is a good 2-D machine and a sonographer who is meticulous and confident," says Clewell.

With multiple pregnancies, you do need to image more frequently. With a single baby in the uterus, you can do it easily and check the size to make sure it is growing frequently. With multiple births, there is no way to check "real" growth. It is hard to clinically tell how the babies are doing.

According to Clewell, "We recommend imaging the babies every three weeks for growth. If you measure a baby more frequently, you will see the baby shrink and grow."

In almost all instances, one fetus may be smaller than the other(s). Clewell explains that this is due to poor placentation. This occurs when one of the babies doesn't get as good of an implant. In cases like this, it is important that you follow the growth and monitor that baby frequently.

"It's important that the scheduler and sonographer allow more time to perform the ultrasound with multiple pregnancies," says Clewell.

For example, with triplets, a complete study checking for growth can take more than an hour, as opposed to a typical single pregnancy, which takes about 30 to 45 minutes. Quads can take up to one and a half hours.

With multiple pregnancies, it is critical to keep straight who's who. "That is one of the hardest things to do," says Clewell. "The membrane between the fetuses are soft and flexible, which it makes it easy to make mistakes. You need to make sure you can somehow distinguish each baby's limbs, neck and body. I recommend making a drawing so that you can record the measurements for each one. You need to make sure you aren't measuring baby A's right limb with baby B's body, etc. So you must take your time."

Patience and making good notes about the fetuses is key – especially when you have many sonographers on staff that the patient sees.

You need to make sure that you know where baby B is so that the next time you image the baby or if a different sonographer does the imaging, they can track the exam all the way through.

Unfortunately, babies don't carry many markers in the womb so that you can tell which is which. You can sometimes tell them apart by gender, and by their location since they tend to stay in the same relative positions, but this doesn't always occur which makes imaging multiples more challenging.

"Another point on multiples that I want to point out is with simple twins," explains Clewell, "Half the time, early on during the first imaging exam, the radiologist will just note that the patient is having twins. They don't take the extra time to tell if they are monochronic and diachronic twins. It's easy to tell early in pregnancy, so all sonographers should take the extra time and make a assessment of the core anacidity of the twins."

Imaging Equipment

As imaging professionals, you are already aware that ultrasound imaging is a technique which uses high-frequency sound waves and a computer to create images of blood vessels, tissues and organs.

Ultrasounds are used to view internal organs as they function and to assess bloodflow through various vessels – with a vaginal transducer, especially in early pregnancy, or with an abdominal transducer in later pregnancy.

While Clewell doesn't recommend using 4-D imaging for multiples, there are certain reasons why it should be considered, according to Gordon Parhar, business unit director with Tustin-Calif.-based Toshiba America Medical Systems.

He explains, "The good thing with 4-D imaging is that you can promote maternal/fetal bonding. Additionally, it can help you check for and determine anomalies, such as a cleft lip, cleft palate, spinal bifida and cardiac anomalies."

It is true that using 3-D and 4-D imaging on twins can be a challenge because of the amount of amniotic fluid between the fetuses, but it can be done. In fact, Toshiba's transducers have been designed especially to accommodate 3-D and 4-D imaging capabilities.

Differential tissue harmonics, the patented technology by Toshiba, allow sonographers to see in deeper organs/structures and it doesn't have the limitation of the poor resolution. This feature is very useful in obstetrics, since you can't expose a pregnant patient to radiation.

In many multiple pregnancy cases, one fetus is dominant. This is called intrauterine growth retardation. When this happens, you may want to see how the blood is flowing in the placenta to ensure that the other fetus is getting what it needs to grow.

Toshiba's machines possess a feature, Advanced Dynamic Flow, which can help you see the profusion. It can help you get a dynamic signal quicker, and as a result, you can get the measurements and results faster, resulting in improved productivity.

Another ultrasound manufacturer, Andover, Mass.-based Philips Medical Systems, has two technologies available that can be particularly useful when imaging multiples.

These unique technologies are xMATRIX, a technology that uses a transducer with 2,400 elements to produce real-time 4-D images, and iSlice, a multislice tool that allows precision slicing of the volume data. This can be displayed in a format of up to 25 slices.

According to Linda Sheets, Philips' global marketing manager, "xMATRIX technology could be useful when imaging multiple gestations to see an abnormality in a limb, like a hand, because you are able to see the motion in 360 degrees. You can take a real-time volume image of that hand, and the sonographer can rotate the image in any position that's desired to get a better view and the ability to diagnose the problem quicker."

At the end of the day, whatever ultrasound machine you use, you must have good image quality.

Sheets stresses that point, saying, "You need a good 2-D image to produce a good 3-D image. A lot is improving with 2-D technology. With that said, diagnostically, you need the best resolution. The [obstetrics] patient will be pleased with the image, as well."

—Desiree B. Mitchell is a Washington-based freelance writer. Questions and comments can be directed to editorial@rt-image.com.