Pregnancy and Birth Sourcebook Part 12

Chorionic villi are tiny finger-like units that make up the placenta (a disk-like structure that sticks to the inner lining of the uterus and provides nutrients from the mother to the fetus through the umbilical cord). They have the same chromosomes and genetic makeup as the fetus.

This alternative to an amniocentesis removes some of the chorionic villi and tests them for chromosomal abnormalities, such as Down syndrome. Its advantage over an amniocentesis is that it can be performed earlier, allowing more time for expectant parents to receive counseling and make decisions. The risks of CVS are higher than with amniocentesis so the risks and benefits of the test must be weighed.

Should I Have This Test?

Your health care provider may recommend this test if you: 150.

Prenatal Medical Tests and Care during Pregnancy * are older than age 35; * have a family history of genetic disorders (or a partner who does); * have a previous child with a genetic disorder or had a previous pregnancy with a chromosomal abnormality; * have had an earlier screening test that indicates that there may be a concern.

Possible risks of this test include: * approximately 1% risk of miscarriage (the risk is higher with the transcervical method than with the transabdominal method); * infection; * spotting or bleeding (this is more common with the transcervical method-see below); * birth defects when the test is done too early in pregnancy.

When Should I Have This Test?

At 10 to 12 weeks.

How Is This Test Performed?

This test is done in one of two ways: * transcervical. Using ultrasound as a guide, a thin tube is pa.s.sed from the v.a.g.i.n.a into the cervix. Gentle suction removes a sample of tissue from the chorionic villi. Some women experience cramping with the removal.

* transabdominal. A needle is inserted through the abdominal wall with ultrasound guidance, and a sample of the chorionic villi is removed. Cramping may be felt with this approach as well.

After the sample is taken, the doctor may check the fetus' heart rate. You should rest for several hours afterward.

When Are the Results Available?

Usually 1 to 2 weeks depending on what the test is being used to look for.

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Pregnancy and Birth Sourcebook, Third Edition Maternal Blood Screening/Triple Screen/Quadruple Screen Why Is This Test Performed?

Doctors use this to test to screen for Down syndrome and neural tube defects. Alpha-fetoprotein (AFP) is a protein produced by the fetus, and it appears in varying amounts in the mother's blood and the amniotic fluid at different times during pregnancy. A certain level in the mother's blood is considered normal, but higher or lower levels may indicate a problem.

This test also looks at the levels of two pregnancy hormones-estriol and human chorionic gonadotropin (HCG)-which is why it's sometimes called a "triple screen" or "triple marker." The test is called a "quadruple screen" ("quad screen") or "quadruple marker" ("quad marker") when the level of an additional substance-inhibin-A-is also measured. The greater number of markers increases the accuracy of the screening and better identifies the possibility of a problem.

This test, which also is called a multiple-marker screening or maternal serum screening, calculates a woman's individual risk based on the levels of the three (or more) substances plus: * her age; * her weight; * her race; * whether she has diabetes requiring insulin treatment; * whether she is carrying one fetus or multiple ones.

Sometimes this test is done along with an ultrasound and blood work during the first trimester, which makes it even more accurate than the second trimester blood work alone.

It's important to note, though, that each of these screening tests determine risk only-they don't diagnose a condition.

Should I Have This Test?

All women are offered some form of this test. Some pract.i.tioners include more parts of it than others. Remember that this is a screening, not a definitive test-it indicates whether a woman is likely to be carrying an affected fetus. It's also not foolproof-Down syndrome, another chromosomal abnormality, or a neural tube defect may go undetected, and some women with abnormal levels have been found 152 Prenatal Medical Tests and Care during Pregnancy to be carrying a healthy baby. Further testing is recommended to confirm a positive result.

When Should I Have This Test?

The blood tests are typically done between 15 and 20 weeks. When first trimester screening is added, the initial tests are done at about 11 to 13 weeks.

How Is the Test Performed?

Blood is drawn from the mother. When first trimester screening is added, an ultrasound is included.

When Are the Results Available?

Usually within a week, although it may take up 2 weeks.

Amniocentesis Why Is This Test Performed?

This test is most often used to detect: * Down syndrome and other chromosome abnormalities; * structural defects such as spina bifida and anencephaly; * inherited metabolic disorders.

Late in the pregnancy, this test can reveal if a baby's lungs are strong enough to allow the baby to breathe normally after birth. This can help the health care provider make decisions about inducing labor or trying to prevent labor, depending on the situation. For instance, if a mother's water breaks early, the health care provider may want to try to hold off on delivering the baby as long as possible to allow for the baby's lungs to mature.

Other common birth defects, such as heart disorders and cleft lip and palate, can't be determined using this test.

Should I Have This Test?

Your health care provider may recommend this test if you: * are older than age 35; * have a family history of genetic disorders (or a partner who does); 153 Pregnancy and Birth Sourcebook, Third Edition * have a previous child with a birth defect, or had a previous pregnancy with a chromosomal abnormality or neural tube defect; * had an abnormal screening test.

This test can be very accurate-close to 100%-but only certain disorders can be detected. The rate of miscarriage with this procedure is between 1 in 300 and 1 in 500. It also carries a low risk of uterine infection, which can also cause miscarriage, leakage of amniotic fluid, and injury to the fetus.

When Should I Have This Test?

Amniocentesis is usually performed between 15 and 20 weeks.

How Is the Test Performed?

While watching with an ultrasound, the doctor inserts a needle through the abdominal wall into the uterus to remove some (about 1 ounce) of the amniotic fluid. Some women report that they experience cramping when the needle enters the uterus or pressure while the doctor retrieves the sample.

The doctor may check the fetus' heartbeat after the procedure to make sure it's normal. Most doctors recommend rest for several hours afterward.

The cells in the withdrawn fluid are grown in a special culture and then a.n.a.lyzed (the specific tests conducted on the fluid depend on personal and family medical history).

When Are the Results Available?

Timing varies; depending on what is being tested for, the results are usually available within 1 to 2 weeks. Tests of lung maturity are often available within a few hours.

Nonstress Test Why Is This Test Performed?

A nonstress test (NST) can determine if the baby is responding normally to a stimulus. Used mostly in high-risk pregnancies or when a health care provider is uncertain of fetal movement, an NST can be performed at any point in the pregnancy after the 26th to 28th week 154 Prenatal Medical Tests and Care during Pregnancy when fetal heart rate can appropriately respond by accelerating and decelerating.

This test may also be done if you've gone beyond your due date. The NST can help a doctor make sure that the baby is receiving enough oxygen and is responding to stimulation. However, an unresponsive baby isn't necessarily in danger, though further testing might be needed.

Sometimes, a biophysical profile is done, which is when an NST and ultrasound are performed, looking at the breathing, movement, amount of amniotic fluid, and tone of the fetus, in addition to the heart rate response.

Should I Have This Test?

Your health care provider may recommend this if you have a high-risk pregnancy, if there are concerns during your pregnancy, or if you have a low-risk pregnancy but are past your due date.

When Should I Have This Test?

An NST may be recommended any time after 26 to 28 weeks, depending on why it is needed.

How Is the Test Performed?

The health care provider will measure the response of the fetus'

heart rate to each movement the fetus makes as reported by the mother or observed by the doctor on an ultrasound screen. If the fetus doesn't move during the test, he or she may be asleep and the health care provider may use a buzzer to wake the baby. You also may be asked to drink or eat to try to stimulate the baby more.

When Are the Results Available?

Immediately.

Contraction Stress Test Why Is This Test Performed?

This test stimulates the uterus with Pitocin, a synthetic form of oxytocin (a hormone secreted during childbirth), to determine the effect of contractions on fetal heart rate. It may be recommended when a nonstress test or biophysical profile indicates a problem and can determine whether the baby's heart rate remains stable during contractions.

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Pregnancy and Birth Sourcebook, Third Edition Should I Have This Test?

This test may be ordered if the nonstress test or biophysical profile indicates a problem. However, it can induce labor.

When Should I Have This Test?

Your doctor may schedule it if he or she is concerned about how the baby will respond to contractions or feels that it is the appropriate test to determine the fetal heart rate response to a stimulus.

How Is the Test Performed?

Mild contractions are brought on either by injections of Pitocin or by squeezing the mother's nipples (which causes oxytocin to be secreted). The fetus' heart rate is then monitored.

When Are the Results Available?

Immediately.

Percutaneous Umbilical Blood Sampling (PUBS) Why Is This Test Performed?

This test obtains fetal blood by guiding a needle into the umbilical cord. It's primarily used in addition to an ultrasound and amniocentesis if your health care provider needs to quickly check your baby's chromosomes for defects or disorders or is concerned that your baby may have another problem, such as a low platelet count or a thyroid condition.

The advantage to this test is its speed. There are situations (such as when a fetus shows signs of distress) in which it's helpful to know whether the fetus has a fatal chromosomal defect. If the fetus is suspected to be anemic or to have a platelet disorder, this test is the only way to confirm this because it provides a blood sample rather than amniotic fluid. It also allows transfusion of blood or needed fluids into the baby while the needle is in place.

Should I Have This Test?

This test may be used: * after an abnormality has been noted on an ultrasound; 156.

Prenatal Medical Tests and Care during Pregnancy * when results from other tests, such as amniocentesis, aren't conclusive; * if the fetus may have Rh disease; * if you've been exposed to an infectious disease that could potentially affect fetal development.

Risks are a.s.sociated with this procedure, such as miscarriage or infection, so the risks and benefits should be discussed with your health care provider.

When Should I Have This Test?

After 18 weeks.

How Is the Test Performed?

A fine needle is pa.s.sed through your abdomen and uterus into the umbilical cord and blood is withdrawn for testing.

When Are the Results Available?

Usually within 3 days.

Talking to Your Health Care Provider Some prenatal tests can be stressful, and because many aren't definitive, even a negative result may not completely relieve any anxiety you might be experiencing. Because many women who have abnormal tests end up having healthy babies and because some of the problems that are detected can't be treated, some women decide not to have some of the tests.

One important thing to consider is what you'll do in the event that a birth defect or chromosomal abnormality is discovered. Your health care provider or a genetic counselor can help you establish priorities, give you the facts, and discuss your options.

It's also important to remember that tests are offered to women- they are not mandatory. You should feel free to ask your health care provider why he or she is ordering a certain test, what the risks and benefits are, and, most important, what the results will-and won't-tell you.

If you think that your health care provider isn't answering your questions adequately, you should say so. Things you might want to ask include: 157.

Pregnancy and Birth Sourcebook, Third Edition * How accurate is this test?

* What are you looking to get from these test results?/What do you hope to learn?

* How long before I get the results?

* Is the procedure painful?

* Is the procedure dangerous to me or the fetus?

* Do the potential benefits outweigh the risks?

* What could happen if I don't undergo this test?

* How much will the test cost?

* Will the test be covered by insurance?

* What do I need to do to prepare?

You also can ask your health care provider for literature about each type of test.

Preventing Birth Defects The best thing that mothers-to-be can do to avoid birth defects and problems with the pregnancy is to take care of their bodies by: * not smoking (and avoiding secondhand smoke); * avoiding alcohol and other drugs; * checking with the doctor about the safety of prescription and over-the-counter medications; * avoiding fumes, chemicals, radiation, and excessive heat; * eating a healthy diet; * taking prenatal vitamins-if possible, beginning before becoming pregnant; * getting exercise (after discussing it with the doctor); * getting plenty of rest; * getting prenatal care-if possible, beginning with a preconception visit to the doctor to see if anything needs to change before you get pregnant.

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