Percutaneous umbilical blood sampling

What it is

With percutaneous umbilical blood sampling (PUBS), a sample of blood is taken from your baby through the vein in the umbilical cord. This diagnostic procedure can detect chromosomal abnormalities, some genetic problems and the presence of infectious disease. PUBS is also known as umbilical vein sampling, fetal blood sampling and cordocentesis.

Your health care provider may offer this procedure if other prenatal diagnostic tests, such as amniocentesis, ultrasound and CVS, have been unable to uncover sufficient information. In the past, PUBS offered the fastest way to gather a sample for chromosomal analysis. New laboratory techniques, such as FISH (see page 304), allow chromosomal evaluation to be completed within a day or two and provide rapid analysis of samples obtained through amniocentesis or CVS. Still, sampling the baby's blood has the potential to revolutionize diagnosis, just as blood tests became so key in adult medicine for helping health care providers in making diagnoses.

In addition, PUBS may be performed to diagnose certain blood disorders and infections and to supply blood transfusions to the baby.

When test results indicate a problem

The unthinkable is happening: Your prenatal test results suggest that your baby may have a problem. Amid the shock, worry and fear, one question surfaces: What now?

To answer that question, start by scheduling a meeting with your health care provider. Talk about the findings and what they might — and might not — mean to you and your baby. If your baby may have a genetic condition, you might want to ask for an immediate referral to a genetic counselor or medical geneticist.

Before meeting with your health care provider, make a list of your questions. Some you might consider:

• How accurate are the test results? Is it possible there's a mistake?

• Can my baby survive this condition? If so, how long is she or he likely to live after birth?

• What problems might be caused by this condition? How might the baby be affected physically? How might the baby be affected mentally?

• Is it likely that my child will need surgeries or other medical treatments to manage the condition? If so, will they be painful? If my baby is in pain, how can the pain be recognized and treated?

• Are there other health care professionals who can give us more information?

• What is involved in caring for a child with this condition?

• Are special programs available to help my child's mental and physical development?

• Is there a support group in our community for families who have a child with this condition? How can we contact parents of children who have a similar condition?

• What are the chances that this condition will affect our next pregnancy?

• What resources are available to us if we decide to end the pregnancy? What counseling services or support groups are available?

Once you've gathered the information, you'll need to make a decision based on your personal circumstances. Consider the emotional and physical aspects of your decision, along with your personal and financial resources.

Here are your options:

• Continue the pregnancy. Make plans for how best to manage the rest of the pregnancy, your labor and delivery, and your baby's treatment after birth. Think about how the baby will affect your family and lifestyle, and, as much as possible, make plans accordingly. Consider seeking out a counselor or support group to help you learn about and meet your child's needs.

• End the pregnancy. The decision to end a pregnancy is never an easy one, even if your baby has a condition that is incompatible with life. Counseling and support groups, both before and after making the decision, can be invaluable in helping you sort out your feelings. Remember, only you can decide if this is the right decision for you. Counselors, health care providers and community resources can provide information, but this most serious of decisions is one you must make.

If you want to consider this option, it's likely that you'll need to gather information quickly. Your health care provider or genetic counselor can help you explore your options.

When it's administered

PUBS is usually done later in the pregnancy, after 18 weeks. Before this point, the umbilical vein is still fragile.

How it's done

As with amniocentesis, for this procedure you lie on your back with your abdomen exposed. Gel is spread over your abdomen and advanced ultrasound is used to locate the umbilical cord. This area on your abdomen is cleansed with antiseptic. With the help of the ultrasound images, your doctor inserts a thin needle through your abdomen and uterus into the umbilical cord vein and withdraws a sample of blood. The sample is then sent to the laboratory for analysis. The entire procedure lasts about 45 minutes to an hour, with the needle in place for only a fraction of the time. Depending on the test, results may be back in as little as two hours.

What the results may tell you

PUBS may provide the following information:

• Chromosomal or other genetic abnormalities. PUBS can detect some of the same chromosomal abnormalities and genetic disorders as can amniocentesis and CVS, such as Down syndrome, and can more directly test for sickle cell disease and hemophilia.

• Blood disorders. The baby's blood sample can be analyzed for signs of anemia and Rh disease. PUBS can also determine the severity of the condition. If the condition is severe, a blood transfusion can be done at the same time. More recently, Doppler ultrasound, which measures the speed of blood flow, may be used as a less risky alternative to diagnosing moderate to severe anemia.

• Infections. If you have an infection, such as toxoplasmosis or rubella, PUBS can determine whether the baby has acquired the infection. However, recent genetic techniques enable health care providers to detect viruses or bacteria directly from amniotic fluid, which is safer.

• Restricted growth. In cases of severe intrauterine growth restriction, PUBS can help determine why your baby isn't growing as he or she should.

Possible concerns

PUBS carries about a 2 percent risk of fetal death. This risk is more than twice that of CVS or amniocentesis. Other risks associated with PUBS include bleeding from the needle entry site — which usually goes away on its own — temporary slowing of the baby's heart rate, infection, cramping and fluid leakage. Call your health care provider if you notice fever, bleeding or leakage of fluid after this procedure.

Reasons to have it done

Because PUBS is somewhat riskier than other prenatal tests, your health care provider will probably offer you other diagnostic options before PUBS. But if you're Rh negative, your baby is Rh positive and a blood test indicates high levels of antibodies against your baby's blood cells, then amniocentesis may be performed to determine whether your baby is developing anemia. When the problem is severe, PUBS can provide a route to deliver a transfusion to your baby.

A few other circumstances might make PUBS the method of choice, for example, if your baby needs a blood transfusion or an infusion of medication.

What happens next

If results are normal, no further testing is usually required. If chromosomal abnormalities are present, you and your health care provider or genetic counselor can discuss your options and arrange for any medical support you'll need.

If your baby has severe anemia, your health care provider may induce early delivery if your baby is mature enough to live outside the uterus. Your baby may be given a blood transfusion through the umbilical cord.

If your baby has an infection, your health care provider will let you know the treatment options available.

Accuracy and limitations of the test

Having an experienced health care provider perform the procedure is critical to the test's success. Thanks to the development of FISH and more sophisticated forms of genetic analysis, the use of PUBS to rapidly diagnose genetic conditions has decreased. However, the procedure still plays an important role in assessing fetal blood disorders and delivering blood transfusions and medication to the baby in the uterus. In the future, this procedure may have other uses.

Late pregnancy tests that assess your baby's well-being

At times, your health care provider may think it's a good idea to check in on how well your baby is doing. Tests that give you and your health care provider a sneak peek at baby's well-being include electronic fetal nonstress and stress tests and biophysical profile scoring.

Electronic fetal nonstress and stress tests

What they are

Fetal nonstress and stress tests assess your baby's well-being by looking at the baby's heart rate. They're typically performed during the last trimester of pregnancy. A baby is considered in good health if his or her heart rate increases after moving and the heart rate is constantly adjusting for the baby's condition. This is what nonstress testing is all about.

Contraction stress tests evaluate the baby's health by monitoring the baby's heart rate in response to contractions induced by medication. Babies in good health will generally tolerate contractions without a significant change in heart rate.

These tests can help your health care provider evaluate the overall health of your baby and verify that continuing the pregnancy doesn't present a significant threat to the baby. One or both may be done, particularly if you have a high-risk pregnancy or if you're past your due date.

When it's administered

These tests are best performed after 28 weeks of gestation. How it's done

The nonstress and contraction stress tests are performed in the following manner:

• Nonstress test. During this test, a belt with transducers attached to it is placed on your abdomen. The transducers are part of the Doppler ultrasound equipment, which measures your baby's heart rate through the use of sound waves. Your health care provider may ask you to push a button each time you feel your baby move, or he or she may record your baby's movement. The heart rate measurement shows up as a graph. Each time the button is pushed, a little arrow shows up on the graph to indicate when the baby has moved.

If your baby doesn't seem to be moving, he or she may be asleep. Your health care provider may wait a few minutes until your baby wakes up or use a buzzer to wake the baby. The test takes about 20 to 40 minutes.

• Contraction stress test. The contraction stress test is performed in much the same way as the nonstress test, using the Doppler ultrasound equipment. During this test, the fetal heart rate is measured while mild contractions are induced. These contractions aren't nearly as uncomfortable as those of labor.

If the contractions aren't occurring on their own, your health care provider may give you an infusion of oxytocin. To be considered adequate, the test usually requires three contractions within a 10-minute period. This test may take one to two hours to complete.

What the results may tell you

About 85 percent of nonstress test results are normal (reactive), which means that your baby's heart rate increased as expected. Abnormal results are termed nonreactive, which means the baby's heart rate didn't accelerate as expected. A

nonreactive test result isn't necessarily a reason to worry. The most common reason for a nonreactive result is that the baby was asleep during testing. Occasionally, abnormal results indicate an oxygen deficiency in your baby.

Results of a contraction stress test are normal (negative) if the baby's heart rate doesn't slow down after contractions. Results are abnormal (positive) if the heart rate consistently slows down after contractions. This may mean your baby isn't getting enough oxygen and may be in danger of dying in the womb. Only 3 percent to 5 percent of contraction stress test results are positive. As scary as this sounds, many positive tests occur in babies who will be normal.

Possible concerns

The nonstress test carries virtually no risk and is safe for both you and your baby. But if you're at risk of premature labor, such as if you're carrying twins, your health care provider may not recommend the contraction stress test.

Reasons to have it done

Your health care provider may recommend a nonstress test if you notice a marked decrease in your baby's movement or if your baby's growth rate seems abnormally slow. Your health care provider may also suggest monitoring your baby's health with a nonstress test once or twice a week after 28 weeks of gestation if you have one of the following conditions:

• A disease that may harm your baby, such as kidney or heart disease

High blood pressure during pregnancy (preeclampsia)

• A history of stillbirth

• Prolonged gestation (You're past your due date.)

• Multiple gestation (You're carrying two or more babies.)

• An abnormal amount of amniotic fluid, indicated by ultrasound examination Contraction stress testing is usually performed if the results from a nonstress test are abnormal.

What happens next

If results of the nonstress test are nonreactive, the test may be prolonged or repeated, or a contraction stress test performed. In one study, about 80 percent of nonstress tests that were nonreactive in the morning became reactive when the test was repeated later in the day.

If a contraction stress test is positive, this doesn't necessarily mean there's a problem. Your health care provider may repeat the test in 24 hours or combine it with other tests, such as biophysical profile scoring (see page 314), to verify whether your baby is in danger. If so, you and your health care provider may decide to induce labor if your baby is old enough to survive. A Caesarean birth may be an option.

Accuracy and limitations of the test

Both tests have very high false-positive rates. A false-positive means the test indicates a problem when there actually is none. Most of the time, abnormal results will be normal when the test is repeated. Because the tests are safe and can be repeated with no harmful effects, they're often the best tools to monitor your baby's health during the last few weeks of pregnancy.

Biophysical profile scoring

What it is

Biophysical profile scoring is another means of monitoring your baby's health during the last trimester. It combines an ultrasound exam with a nonstress test. The tests usually assess five different aspects of your baby's health, including:

• Breathing movements (Your baby doesn't breathe air inside the uterus, but breathing movements move small amounts of fluid in and out of the lungs.)

• Body movement

• Amount of amniotic fluid

Each of these factors is given a score of 0 or 2, and the scores are added together to achieve a total from 0 to 10.

When it's administered

This test may be used as early as the 26th week of gestation. How it's done

Your baby's heart rate is measured using a nonstress test. The other four factors — breathing, movement, muscle tone and amniotic fluid — are evaluated with ultrasound. If a factor is normal, it receives an individual score of 2. If it's absent or less than expected, it receives a score of 0.

What the results may tell you

A score of 6 or less may indicate your baby is suffering from a lack of oxygen. The lower the score, the greater the cause for concern. In a large study of over 26,000 high-risk pregnancies, almost 97 percent had biophysical profile scores of 8 or more.

Possible concerns

Both the nonstress test and ultrasound are considered to be very safe. Some medications may reduce the biophysical profile score.

Reasons to have it done

The reasons for having a biophysical profile done are similar to those for having the nonstress and stress tests. It helps you and your health care provider keep track of your baby's health before delivery, particularly if you have a high-risk pregnancy.

What happens next

Depending on your score, your health care provider may recommend one of several courses of action. If you have diabetes or are past your due date and the score is 8 or above, testing may be repeated once or twice a week. If the score is 6 or below, the test may be repeated to confirm the score. If necessary, your health care provider may recommend that the baby be delivered ahead of your due date.

Accuracy and limitations of the test

The false-positive rate for any individual factor of the biophysical profile is high, but when all factors are combined, the false-positive rate decreases. Having a low score doesn't necessarily mean that your baby is in trouble. It may just mean that you need special care throughout the rest of your pregnancy.

Herbal Healing For Everyone

Herbal Healing For Everyone

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