Prenatal Testing

Every mother hopes for a healthy baby, but these dreams are frequently accompanied by moments of worry about the baby's health. Concerns like these are completely normal. Fortunately, there are many prenatal tests that can help a pregnant women assess the health and progress of her growing baby. As an expectant parent, it is important to take the time to educate yourself about these tests and to think about what you would do if a health problem is detected in either you or your baby.

The following has been adapted from the websites listed at the bottom of the page.

Prenatal care, or regular visits to your doctor or midwife, are very important. A typical schedule of prenatal care includes visiting your doctor or midwife about once each month during your first six months of pregnancy, every two weeks during the seventh and eighth month of pregnancy, and weekly in the ninth month of pregnancy. If you are over 35 years old or your pregnancy is high risk because you have certain health problems (like diabetes or high blood pressure), your doctor or midwife will probably want to see you more often.

While you are pregnant your doctor or midwife may suggest a number of laboratory tests, ultrasound exams, or other screening tests. The aim is to detect birth defects such as neural tube defects, chromosome abnormalities, genetic diseases and other conditions.

There are both invasive and non-invasive methods of diagnosing a problem before birth. If an abnormality is suspected by a non-invasive procedure, a more invasive technique may need to be offered to get more information.

Examination of the mother's uterus from outside the body. (i.e. feeling the mother's 'stomach'.)
Ultrasound detection - Commonly used to check the baby's sex, to look for twins, and also to check for any abnormal development.
AFP screening can check levels of alpha fetoprotein, β-hCG, and estriol in the mother's serum.
Detection of fetal blood cells in maternal blood. With this technique it is technically possible to obtain a sample of the baby's DNA using blood cells from the fetus, that have made their way into the mother's bloodstream.

Chorionic villus sampling - Involves getting a sample of the chorionic villus and testing it. This can be done earlier than amniocentesis, but is a more risky procedure.
Amniocentesis - This can be done once enough amniotic fluid has developed to sample. Cells from the baby will be floating in this fluid, and can be separated and tested.
Embroscopy and fetoscopy - These involve putting a probe into a women's uterus to observe (with a video camera), or to sample blood or tissue from the baby.

During your first visit to your health care provider for prenatal care, you can expect to have a full physical, including a pelvic and rectal examination, and a blood sample taken.

Your blood type and Rh factor. If your blood is Rh negative and your partner's is Rh positive, you may develop antibodies that prove dangerous to your fetus. This can be treated through a course of injections.
Anemia (a low red blood cell count) to make sure you're not iron deficient
Hepatitis B, syphilis, and human immunodeficiency virus (HIV)
Immunity to German measles (rubella) and chickenpox (varicella)
Cystic fibrosis. Health care providers now routinely check for this even when there's no family history of the disorder.

To do a Pap smear, your health care provider uses what looks like a very long mascara wand or cotton swab to gently scrape the inside of your cervix (the opening to the uterus that's located at the very top of the vagina). This does not hurt but some women say they feel a little twinge, but it only lasts a second. This tests for STD's such as chlamydia and gonorrhea and for cervical cancer.

After the initial visit, your health care provider will order other tests based on, among other things, your personal medical history and needs. Some of these tests may include:

Urine tests for sugar, protein, and signs of infection. The sugar in urine indicates gestational diabetes - diabetes that occurs during pregnancy; the protein can indicate preeclampsia - a condition that develops in late pregnancy and is characterized by a sudden rise in blood pressure and excessive weight gain, with fluid retention and protein in the urine.
Group B streptococcus (GBS) infection. GBS bacteria are found naturally in the vaginas of many women and can cause serious infections in newborns. This test involves swabbing the vagina, usually between the 35th and 37th weeks of pregnancy.
Sickle cell trait tests for women of African or Mediterranean descent, who are at higher risk for having sickle cell anemia - a chronic blood disease - or carrying the trait, which can be passed on to their children.

Following is a list of other tests that are now performed almost routinely in the United States as well as those that are performed only in high-risk pregnancies or if the health care provider suspects an abnormality in the fetus.

Screening tests measure the risk of having a baby with some genetic birth defects. The benefit of screening tests is that they do not pose any risk to the fetus or mother. But screening tests cannot tell for sure if the baby has a birth defect. Birth defects are caused by problems with a baby's genes, inherited factors passed down from the mother and the father. Birth defects can also occur randomly in people with no family history of that disorder. Women over the age of 35 have the greatest risk of having babies with birth defects.

Glucose screening checks for gestational diabetes, a short-term form of diabetes that develops in some women during pregnancy. Gestational diabetes occurs in 1% to 3% of pregnancies and can cause health problems for the baby. This test involves drinking a sugary liquid and then having your blood drawn after an hour. If the sugar level in the blood is high, you'll have a glucose-tolerance test, which means you'll drink a glucose solution on an empty stomach and have your blood drawn once every hour for 3 hours. The American Diabetes Association suggests that in order to confirm diabetes, these tests be performed at different times.

Screening for gestational diabetes usually takes place at 12 weeks for women at higher risk of having the condition, including those who:

All other pregnant women are tested for diabetes at around 24 to 28 weeks. But if you've had high sugar in two routine urine tests, your health care provider may order it earlier.

The best time to receive this test is between 18 and 20 weeks of pregnancy. Most major problems with the way your baby might be formed can be seen at this time. For additional information please visit the link Ultrasounds.

This blood test can be called by many different names including multiple marker screening test, triple test, quad screen, and others. This test is usually given between 15 and 20 weeks of pregnancy. your health care provider will take a sample of your blood and checks for birth defects such as Down syndrome, trisomy 18, or open neural tube defects.

This test, which also is called a multiple-marker screening or maternal serum screening, calculates a woman's individual risk of birth defects based on the levels of the three (or more) substances plus her age, weight, pace, and whether she has diabetes requiring insulin treatment.

This is a relatively new screening test that can be done between 11 and 14 weeks of pregnancy. It uses an ultrasound and blood test to calculate the risk of some birth defects.

Diagnostic tests can give definite "yes" or "no" answers about whether your baby has a birth defect. But, unlike screening tests, they are invasive or come with a risk of miscarriage. Amniocentesis and chorionic villus sampling (CVS) are the two most commonly used. Both tests are more than 99% accurate for finding these problems. These tests also can tell you your baby's sex. In most cases, results take about two weeks.

This test is performed in pregnancies of at least 16 weeks. It involves your doctor inserting a thin needle through your abdomen, into your uterus, and into the amniotic sac to take out a small amount of amniotic fluid for testing. The cells from the fluid are grown in a lab to look for problems with chromosomes. This test can be very accurate - close to 100%, but only certain disorders can be detected. According to the Centers for Disease Control and Prevention (CDC), the rate of miscarriage with this procedure is between 1 in 400 and 1 in 200.

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 newer 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.

This test is performed between 10 and 12 weeks of pregnancy. The doctor inserts a needle through your abdomen or inserts a catheter through your cervix in order to reach the placenta. Your doctor then takes a sample of cells from the placenta. These cells are used in a lab to look for problems with chromosomes. About 1 in 200 women have a miscarriage as a result of this test.

This test obtains fetal blood by guiding a needle into the umbilical vein. 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 if he or she is concerned that your baby may be anemic.

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.

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 when fetal heart rate can appropriately respond by accelerating and decelerating.

If you've gone beyond your due date, this test also uses external fetal monitoring to determine fetal movement. The NST can help a doctor make sure that the baby is receiving enough oxygen and that the nervous system is responding. However, a nonresponsive baby doesn't necessarily mean that the baby is in danger.

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

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's usually recommended when a nonstress test indicates a problem and can determine whether the baby's heart rate remains stable during contractions.

The option to continue a pregnancy or abortion is the main choice after most prenatal testing.

Are the risks of prenatal diagnosis, such as amniocentesis worth the potential benefit?
Some fear that this may lead to being able to pick and choose what children parents would like to have. This could lead to choice in sex, physical characteristics, and personality in children.
Knowing about certain birth defects, such as spina bifida, before birth may give the option of fetal surgery during pregnancy, or to assure that the appropriate treatment and/or surgery be provided immediately after birth.
Are mentally or physically different children less valuable in our society?
How to ensure that information about testing options is given in a non-directive and supportive way.
That parents are well informed if they have to consider abortion vs. continuing a pregnancy.

Final Comment

Some prenatal tests can be stressful, and because many are not definitive. Since many women who have abnormal tests end up having healthy babies many of the problems that are detected can not be treated, some women decide not to have some of the tests.

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

Although your health care provider may recommend these tests, it is ultimately up to you to decide whether to have them. To decide which tests are right for you, it is important to carefully discuss with your health care provider why he or she is ordering a certain test, what the risks and benefits are, what the results will and will not tell you, how reliable they are, the potential risks, and your options and plans if the results indicate a disorder or defect. If you think that your health care provider is not answering your questions adequately, you should say so.

It is important to remember that tests are offered to women but they are not mandatory.

Please visit the link Prenatal Care for additional information.

Prenatal Testing and Prenatal Tests

Doctor Visits and Prenatal Visits

Additional Information