Prenatal Tests
You'll be offered many prenatal tests during your pregnancy. Some may be called "routine." It's important to understand that "routine" and "required" are two different things!
Weigh the benefits and the risks of each procedure before deciding to have it. Talk to your midwife or doctor about each test. Ina May's Guide to Childbirth
has excellent information on weighing pros and cons of prenatal tests.
Read about each test, or quickly jump to a specific test here:
Urine Test
Weight Check
Prenatal Workup (Blood Tests)
Pap Smear
Ultrasound
Glucose Challenge Test
Strep B
Internal Exam (Cervix check)
CVS
Triple Screen
Genetic Tests
Amniocentesis
Nuchal Fold Screening
Note: This information page can't completely and thoroughly cover all prenatal tests. I urge you to speak with your care provider and research further about your specific concerns.
Procedures done on your or your baby are your choice! Get the information you need.
I'm continuously working to add more relevant information. Contact me if you'd like more information or don't see the prenatal tests you are looking for. I'll try to get more information to you.
Prenatal Tests You May Be Offered
Your feelings about prenatal tests
Urine Dip
For this test you will probably be asked to collect a urine sample in a cup. A small strip of paper with reactive boxes (the dipstick) is dipped into the sample. The dipstick usually shows the presence of several things:
- Glucose: sugar that has spilled into urine. Its presence in urine may indicate diabetes. Eating a very sugary meal just before the test may cause glucose to be present in the urine.
- Ketones: produced when the body is breaking down fat for energy instead of sugars. Ketone levels are a way to monitor for diabetes.
- Blood: Trace amounts of blood in the urine are normal. A larger amount may indicate an infection or problem in the urinary tract.
- Protein: protein in the urine can be an early indicator of pre-eclampsia. Trace amounts of protein in the urine can be normal in late pregnancy.
- PH: PH levels can indicate a possible urinary tract infection.
- Leukocytes: Leukocytes are white blood cells. They can be a sign of infection. A simple cold can cause leukocytes to be present in the urine. Leukocytes may indicate that the body needs more rest.
- Some urine dips may do additional checks.
Many care providers routinely do a urine dip prenatal tests at each appointment. The test is non-invasive. You may feel anxious about having to "pee on demand" or having to "pee in a cup." The test may cause anxiety after positive result. Many factors of this test are influenced by your diet. It's a good reminder to eat carefully and get enough rest.
Weight Check
This isn't really one of the prenatal tests but it is very standard. You'll be asked to stand on a scale and your weight will be added to your chart. Note that using different scales may give an inaccurate picture of weight gain. Gaining a lot of weight very suddenly could indicate a problem such as pre-eclampsia.
Weight gain during pregnancy is a hotly debated topic. Most care providers monitor weight gain. Others do not unless they feel there is a problem. Some midwives won't weigh you if the checks are causing a lot anxiety.
Some women gain weight steadily throughout pregnancy. Others have a more irregular weight gain. Most weight tends to be gained in the last two months of pregnancy as the baby is growing rapidly.
A pound a week in late pregnancy is generally considered normal. 25-35 pounds is considered "ideal." Anxiety about weight gain seems to be common in women and is a negative aspect of monitoring weight.
Prenatal Workup
This test is often done at your first prenatal appointment. If you see a midwife you may have this done with your backup obstetrician. The test involves having multiple vials of blood drawn (usually four or five).
Most women opt to have a prenatal workup done. Side effects from having a lot of blood drawn can be nausea and sometimes fatigue. Some women may be opposed to having an HIV/AIDS screening. You may request a copy of your prenatal workup results for your records. Your midwife, doctor, or nurse can help you read the results from these prental tests.
The prenatal workup screens for diseases and infections that could harm your baby, including sexually transmitted diseases. You will be offered screening for HIV/AIDS. Some doctors are beginning to require this testing.
These prenatal tests will also check for anemia, your blood type, and for your Rh factor. The prenatal workup often screens for rubella antibodies, and it may screen for other antibodies as well. Here is some more detailed information:
Complete blood count:A white blood cell count, red blood cell count, hemoglobin, hematocrit, MCV (mean corupuscular volume, size and shape of red blood cells, this can indicate some anemias), platelet count, ESR rate (erythrocyte sedimentation rate, elevated rate normally means anemia, infection, or chronic inflammations).
Also: A glucose test, creatinine (which can indicate how your kidneys are), blood salt measures, uric acid levels (kidneys again), albumin (this is a protein, low levels are not good), globulin (high levels can indicate chronic inflammation), calcium (high blood count not good), SGPT (this can give an indication of liver function), LDH (lactate dehydrogenase, very high levels are bad), Bilirubin, GGT (liver again).
The test also tells you your blood type and your rh factor. They may do an indirect-coombs if you are Rh-, which tests to see if your body is sensitized.
Pap Smear
A pap during pregnancy is most often done at the first appointment you see your care provider. Not all care providers do a pap during pregnancy. It's one of the more uncomfortable prenatal tests.
It is done in the same way as a normal pap. You lie on a table with your feet in stirrups while the doctor inserts a speculum into your vagina. The doctor takes a swap around the cervix and places a specimen on a glass slide. The slide is sent to a lab to examine for abnormal cell growth. This could indicate cancerous cells.
This is a "routine" test in many doctor's offices. It is very uncomfortable for some women. You may feel fear or other overwhelming feelings. There should always be a nurse in the room with the doctor and you can bring someone with you as well. Do not let a doctor or nurse tell you that you can't have someone there with you. It is your right to decline having a pap done.
You and your practitioner should be aware that paps during pregnancy and early postpartum have a higher rate of false positives. As a result, some midwives recommend no pap during pregnancy, and that women wait until around six months postpartum to have one done.
Ultrasound Prenatal Tests
During pregnancy these prenatal tests give a "glimpse inside" the womb. In early pregnancy a vaginal ultrasound can be done. A special scanner is inserted into the vagina (some doctors allow the woman to do this herself) and the ultrasound performed.
Most ultrasounds are done by passing a scanner back and forth over the abdomen. Ultrasound is actually sound waves that are transmitted to the body and bounce back to the receiver after hitting soft tissues. The returned data is calculated by the machine and creates a "picture" on a monitor. Ultrasound has many, many indications during pregnancy:
- Determining due date (this is most accurate early in pregnancy)
- Estimating the size of the baby
- Checking the position of the baby (a skilled practitioner can tell this information by palpitating your abdomen.)
- Checking the position of the placenta (an placenta in an odd location early in pregnancy often corrects itself before the baby's birth)
- Checking for multiple pregnancy (it is very rare for surprise multiples to be born. Even without ultrasound multiples are usually diagnosed during pregnancy.)
- Checking fetal growth rate by doing multiple scans over a period of time.
- An ectopic, or "tubal" pregnancy can be detected by ultrasound.
- Checking the volume of amniotic fluid around the baby.
- Ultrasound is also used to guide for other procedures such as amniocentesis and external version.
There are now 3D and 4D ultrasounds as well as the traditional 2D. 3D ultrasounds are even cropping up at freestanding ultrasound "photography centers." You can pay (normally $100+) to have a scan of your baby done. Theses centers are not monitored or licensed by any agency so these ultrasounds don't really count as prenatal tests.
Many women and families feel that ultrasound also helps them bond. You may enjoy seeing your baby on the screen. You may also want to know your unborn baby's gender (just remember sometimes the ultrasound technician gets it wrong!). A certain sense of excitement often surrounds an ultrasound scan.
Ultrasound is being debated by some because the safety of the procedure is not 100% assured. Ultrasound heats cells slightly. Proponents of ultrasound argue that the heating is within the range of normal for human fetal cells. Others say that there is no way to be sure that even a slight rise in temperature is safe.
Another issue is the effect of the sound waves themselves on cells. Studies on mice at a similar developmental stage to human fetuses show that ultrasound can effect the growth of cells and increase their rate of death (as reported by Dr. Patrick Brennan in New Scientist June '99)
Occasionally ultrasound scans can give a "false positive" for uterine conditions. Diagnosing twins when there is just one baby, diagnosing that a pregnancy is not viable when it is, and diagnosing disorders that are not present can happen occasionally. The instance of these misdiagnosed prenatal tests are not common, however.
Many feel that ultrasound as prenatal tests should only be used where indicated. Examples include a baby who does not seem to be growing in utero or to check the volume of fluid around the baby. These experts discourage routine ultrasound on all pregnant women.
Some mothers find scans to be distancing. You could develop anxiety when a problem is discovered. You may worry needlessly over a problem that turns out to be nothing. The range of emotions involved with ultrasound is complex.
Glucose Challenge Prenatal Tests/Glucose Tolerance Prenatal Tests
The glucose challenge test shows the possibility of gestational diabetes. These prenatal tests are normally done between 24-28 weeks.
You are required to drink a bottle of very sweet liquid. It is compared to a very, very sweet soda. Your blood is taken (normally a finger prick) just before you drink, then you wait for an hour and your blood is taken again. If your blood sugar level is above a certain number, you are asked to come back for another test.
The Glucose Tolerance Test is a longer version of the Glucose Challenge Test. You are required to fast 8-12 hours beforehand. Then you drink twice as much of the liquid, or a liquid with twice the sugar concentration. You will have your blood taken before the test. Once every hour for three hours after the test you will have your blood taken again. The levels of your blood sugar at each hour will determine if you are diagnosed with gestational diabetes.
Drinking the liquid from the tests may make you feel nauseous and woozy. The effect of the sugar rush on the baby is not considered harmful. You could feel that their babies are upset by the huge influx of sugar. You may also feel weak and ill after these prenatal tests due to the long fast required beforehand.
Some care providers do not do the glucose test routinely, believing that unless there seems to be a problem it is better not to force mothers and babies to have an unpleasant test. Persistent glucose in the urine is one indication that gestational diabetes may be a problem.
Another option for the glucose challenge test is using a glucometer. This instrument measures blood sugar level in diabetic patients with a simple finger prick.
Strep B Swab/Test
The Beta-Strep test (called step b, beta-strep, b-strep) is simple compared to many prenatal tests. A long cotton swab is swept around the vagina to gather fluid. The fluid is sent to a lab to be cultured. The test looks for the presence of beta-strep bacteria. This bacteria is present normally in around 20% of women. The test is normally done around 36 weeks.
Betra Strep bacteria can possibly cause infection in the newborn. If you test positive for strep-b, your care provider will probably recommend you have intravenous antibiotics during the course of labor. If you are planning a homebirth, having this test come back positive could cause you to be risked out.
Dr. Michel Odent, a well known French obstetrician, reports that it is very rare for full term health babies to be affected by strep. B bacteria in the vagina. Premature and low birth-weight babies are more at risk. Several recent studies have shown that an antibiotic spray may be as effective as intravenous antibiotics at preventing newborn infection.
The test may make you uncomfortable since it is done with a vaginal swab. A nurse should always be in the room with you and your doctor. You can take someone with you to the test.
Having the test culture positive may be devastating for women planning a homebirth who are "risked out" to be in the hospital with antibiotics.
Women in the hospital who were hoping to move around may feel anger, frustration, and increased pain due to having the IV attached and possibly hampering movement. Antibiotics sometimes complicate breastfeeding by allowing thrush (yeast) to grow easily. This is because the antibiotics kill the helpful bacteria that keep yeasts in check when they kill the harmful bacteria. Thrush can make breastfeeding extremely painful, but is treatable.
Internal/Cervical Exams
To do an "internal," your doctor or midwife will have you lie on your back. You put your feet in stirrups or you may be asked to spread your legs. Your care provider will then use a gloved hand to feel your cervix (in the vagina). This is usually done in late pregnancy to determine if any dilation or effacement is happening.
An internal can be helpful in cases of suspected preterm labor. It is sometimes reassuring to you to know what your cervix is doing.
Internals are a notoriously bad way of predicting when labor will start. They cause you to feel anxious if you are not effaced or dilated at all. In reality, you could have no dilation or effacement in the morning and be in labor that night. Or you could be 3cm dilated and 100% effaced and stay that way for two weeks.
Internal prenatal tests can introduce germs to the vagina, which is a particular concern if the water bag has ruptured. Internal exams can also be very hard for women that have feelings of violation with such intimate exams. If you do not feel comfortable with a routine internal during pregnancy, tell your care provider. You may also want to request minimal internal exams during labor. It is your body.
CVS Prenatal Tests
CVS stands for Chorionic Villus Sampling. It is generally done between 10-12 weeks of pregnancy. CVS tests for certain genetic conditions and chromosomal abnormalities. It cannot test for neural tube defects.
The procedure involves a sample of cells being taken from your baby's placenta. A long, thin needle is inserted into the placenta to gently suction out a sample - the amniotic sac is not disturbed. The needle can be inserted through the abdomen (as with an amnio) or through the cervix.
You will only be offered this test if you are considered to be at increased risk for one of the disorders that it screens for.
The advantages and disadvantages of CVS prenatal tests are similar to those of amniocentesis. The risk of miscarriage is thought to be slightly higher (between 1:100 and 1:200). All the emotional implications involved with amnio are present with CVS.
Advantages are that the CVS prenatal tests can be done earlier, giving you more time to prepare. It is also done in the first trimester, which some women find reassuring if they decide to terminate a pregnancy. You can also find out your baby's gender from the test, which a small advantage to some!
Triple Screen Prenatal Tests (Alpha Feto Protein)
This blood test can identify women who have a higher risk of carrying a baby with certain birth defects. These include neural tube defects and chromosomal abnormalities. It is usually done 15-18 weeks. If results are positive, an ultrasound or amniocentesis will be offered for further diagnosis.
Triple screen prenatal tests have a high rate of false positives. They also gives false negatives.
The test can help women that would consider terminating an abnormal pregnancy. It may cause women who would continue their pregnancy regardless undue stress. The high false positives also cause anxiety. Having to move to more invasive testing to investigate a positive result can also cause tension and these tests have their own unique set of considerations. Jump to amniocentesis or ultrasound.
Genetic Prenatal Tests
You may have prenatal tests done to screen for increased possibility of certain genetic conditions. Cystic Fibrosis screenings are offered routinely by some doctors now. Others tests may screen for increased risk of Sickle Cell anemia, Tay-Sachs disease, and other genetic conditions.
These prenatal tests are usually blood tests and involve having one or two vials of blood drawn. Common side effects may include bruising at the site where the blood is drawn and nausea. Some women feel weak after having blood drawn.
Waiting on test results can cause anxiety. They only screen for an increased risk of having a baby with the disorder, and are not completely positive as to whether the baby currently being carried has the disorder. You may wish to opt out of these prenatal tests.
If you have a history of the disorder in your family, however, you may choose to have the screening done.
Amniocentesis
This test requires a thin needle to be inserted through the mother's abdomen and into the amniotic fluid surrounding the baby in utero. The technician performing the "amnio" is guided by ultrasound as the needle is inserted. A small sample of amniotic fluid is sampled and tested. The test is most often offered to women over 35 becoming mothers. Mothers with indications of possible birth defects (including a positive triple screen) are usually offered an amnio as well.
The test can indicate chromosomal abnormalities and some types of birth defects, including neural tube defects, and genetic disorders. It is considered very accurate for diagnosing these disorders. It can help a woman decide if she wants to continue a pregnancy or not. If the pregnancy is continued it can help her and her care providers prepare for the arrival of the baby.
There is a risk of miscarriage (1:200 or less risk, March of Dimes) with amniocentesis. The test is invasive and can introduce infection. Results can take up to around two weeks. The long wait on results can cause women and families a lot of anxiety. For women who would not terminate a pregnancy even with results indicating a problem, the amnio can a lot of stress.
It is hard to choose if you should or should not have an amnio. The thought process is complicated and weighed with a lot of emotion. If you are considering an amnio, do not hesitate to ask each and every question you have on your mind - understand all the analysis and prenatal tests involved with the amnio. You can also request to talk to a perinatologist or another specialist about amniocentesis. A closely related procedure that can be done earlier is a CVS.
Nuchal Fold Screening
This test examines the translucent (clear) space at the back of your baby's neck - your baby's nuchal fold. The timing of the test begins at 11 weeks gestation and ends the day before 14 weeks gestation. The test can show the possibility of Down's syndrome and other chromosomal defects.
Nuchal fold screening is done by abdominal ultrasound. Your ultrasound technician will first measure your baby to access approximate gestational age. Then she will measure your baby's nuchal fold area with calipers. This measurement is put into a formula containing other factors, including baby's gestational age and your age, that will give a statistical probability that your baby will have certain chromosomal defects.
The test is not conclusive for chromosomal defects, and is usually given to indicate if more invasive tests (such as amniocentesis or CVS) should be done. It is about 80% accurate - that is, about 80% of babies with a chromosomal defect will be detected by the screening. The remaining 20% of babies with an abnormality will show "normal" results on the screening.
The test is non-invasive and considered to be safe. It may be a good option for women considering an amnio or CVS but aren't sure they want to go with such an invasive route. The screening gives them an idea about whether they should go ahead with the more invasive testing.
Some women may have to wait up to 10 days for the baby's measurements to be sent off to be analyzed statistically. This can cause some anxiety. Other women may be falsely reassured that their baby has no chromosomal abnormalities when, in fact, their baby was one of the 20% of "false negatives" the test can produce.
Some doctors are beginning to offer the nuchal fold screening in conjunction with blood prenatal tests. They call this the First Trimester Combined Screening Test. They generally offer two blood tests that look for the amount of two proteins in your blood (freeBeta-hcg and PAPP-A). Including these blood tests bring accuracy to about 90%.
Inclusion of a fourth marker can bring accuracy up to 97%. This fourth marker is the nasal bone. If it is not present between 11 and 14 weeks, there is an increased risk of chromosomal abnormality. Sometimes these screenings are also viewing in conjunction with the triple screen.
A woman faced with a positive result from these prenatal tests will have to decide if she wants to continue her pregnancy. Facing this situation is very hard. Your Feelings about Prenatal Testing explores these feelings in more depth.