Common Tests During Pregnancy
These are some of the more common tests done during pregnancy.
First trimester prenatal screening tests
First trimester screening is a combination of fetal ultrasound and maternal blood testing. It can help find
out the risk that the fetus has certain birth defects. Screening tests may be used alone or with other
tests.
First trimester screening has 3 parts.
Ultrasound test for fetal nuchal translucency (NT)
Nuchal translucency screening uses an ultrasound test to check the area at the back of the fetal neck for
extra fluid or thickening.
Two maternal serum (blood) tests
These tests measure 2 substances found in the blood of all pregnant women:
Pregnancy-associated plasma protein screening (PAPP-A). This is a protein made by the placenta in
early pregnancy. Abnormal levels are linked to a higher risk for chromosome problems.
Human chorionic gonadotropin (hCG). This is a hormone made by the placenta in early pregnancy.
Abnormal levels are linked to a higher risk for chromosome problems.
When used together, these tests have a greater ability to find out if the fetus might have a genetic birth
defect such as Down syndrome (trisomy 21) and trisomy 18.
If the results of these tests are abnormal, your healthcare provider will suggest genetic counseling. You
may need more testing. That may include chorionic villus sampling, amniocentesis, cell-free fetal DNA,
or other ultrasounds.
Second trimester prenatal screening tests
Second trimester prenatal screening may include several blood tests. These are called multiple markers.
They give information about a woman's risk of having a baby with certain genetic conditions or birth
defects. Screening is often done by taking a sample of your blood between the 15th and 20th weeks of
pregnancy. The 16th to 18th is ideal. The multiple markers are listed below.
Alpha-fetoprotein screening (AFP)
This blood test measures the level of alpha-fetoprotein in your blood during pregnancy. AFP is a protein
normally made by the fetal liver. It is in the fluid around the fetus (amniotic fluid) and crosses the
placenta into your blood. The AFP blood test is also called MSAFP (maternal serum AFP).
Abnormal levels of AFP may be a sign of:
Open neural tube defects (ONTD) such as spina bifida
Down syndrome
Other chromosome problems
Problems in the abdominal wall of the fetus
Twins. More than one fetus is making the protein.
An incorrect due date. The levels of AFP vary throughout pregnancy.
Other markers are:
hCG. This is human chorionic gonadotropin hormone. It is made by the placenta.
Estriol. This is a hormone made by the placenta.
Inhibin. This is a hormone made by the placenta.
Abnormal results of AFP and other markers may mean you need more testing. An ultrasound is often
done to confirm the dates of the pregnancy. It also looks at the fetal spine and other body parts for
problems. You may need an amniocentesis for accurate diagnosis.
Multiple marker screening is not diagnostic. This means it is not 100% accurate. It is only a screening test
to find out who should be offered more testing for their pregnancy. The tests show false-positive results.
This means they show a problem when the fetus is actually healthy. Or the results may be false negative.
This means they show that the fetus is normal when the fetus actually does have a health problem.
Having both first and second trimester screening tests done makes it more likely to find a problem if
there is one than using just one screening alone. As many as 19 out of 20 cases of Down syndrome can
be found when both first and second trimester screening are used.
What is an amniocentesis?
An amniocentesis is a test that takes a small sample of the amniotic fluid. It is done to diagnose
chromosome problems and open neural tube defects (ONTDs) such as spina bifida. The test can also
look for other genetic problems and disorders if you have a family history of them. These other results
also depend on the lab doing the testing. An amniocentesis is generally offered to women between the
15th and 20th weeks of pregnancy who are at higher risk for chromosome problems. This includes
women who have had an abnormal maternal blood screening test. The test may have indicated a higher
risk for a chromosome problem or neural tube defect.
How is an amniocentesis done?
An amniocentesis involves putting a long, thin needle through your abdomen into the amniotic sac. The
healthcare provider withdraws a small sample of the amniotic fluid. The amniotic fluid has cells shed by
the fetus,. These cells have genetic information. The specific details of each test vary slightly, but an
amniocentesis often follows this process:
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The healthcare team cleans your belly (abdomen) with an antiseptic.
The healthcare provider may use a local anesthetic to numb the skin.
The provider uses ultrasound to help guide a hollow needle into the amniotic sac.
The provider withdraws a small sample of fluid to be sent to a lab.
After the test, don't do any strenuous activity for 24 hours. You may feel some cramping during or after
the amniocentesis.
If you are carrying twins or other multiples, you will need sampling from each amniotic sac to study each
baby.
The fluid sample is sent to a genetics lab so that the cells can grow and be tested. AFP is also measured
to rule out an open neural tube defect such as spina bifida. AFP is a protein made by the fetus and is in
the fluid.
Discuss the risks of this procedure with your healthcare provider. Sometimes the amniocentesis can't be
done. It depends on the position of the baby, the placenta, the amount of fluid, and your anatomy.
What is a chorionic villus sampling (CVS)?
Chorionic villus sampling (CVS) is a prenatal test. It involves taking a sample of some of the placental
tissue. This tissue often has the same genetic material as the fetus. It can be tested for chromosome
problems and some other genetic problems. The test can also look for other genetic problems and
disorders if you have a family history of them. These other results also depend on the lab doing the
testing. Unlike amniocentesis, CVS does not give information on neural tube defects such as spina bifida.
For this reason, women who have CVS also need a follow-up blood test between 16 and 18 weeks of
their pregnancy to screen for neural tube defects.
How is CVS done?
CVS may be offered if you are at higher risk for chromosome problems. You may also be offered it if you
have a family history of a genetic problem that is testable from the placental tissue. CVS is usually done
between the 10th and 13th weeks of pregnancy. The exact method for CVS an vary, but the procedure
involves putting a small tube (catheter) through your vagina and into your cervix. It usually follows this
process:
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The healthcare provider uses ultrasound to guide the catheter into place near the placenta.
The provider removes tissue using a syringe on the other end of the catheter.
For a transabdominal CVS, the provider puts a needle through your abdomen and into the
uterus to take a sample of cells from the placenta.
You may feel some cramping during and after the CVS procedure.
If you are carrying twins or other multiples, you often will need sampling from each placenta. But CVS is
not always advised for multiples because the procedure is complicated and the placentas may not be in
a good position to get a sample.
The tissue samples are sent to a genetic lab to grow and be tested. Results are often available in 10 days
to 2 weeks, depending on the lab.
Some women may not be candidates for CVS, or they may not get results that are 100% accurate,. They
may need a follow-up amniocentesis. In some cases an active vaginal infection such as herpes or
gonorrhea will prohibit the procedure. Other times the healthcare provider takes a sample that does not
have enough tissue to grow in the lab. That may cause incomplete or inconclusive results.
Discuss the risks of CVS with your healthcare provider.
What is fetal monitoring?
During late pregnancy and during labor, your healthcare provider may want to watch the fetal heart rate
and other functions. Fetal heart rate monitoring is a way of checking the rate and rhythm of the fetal
heartbeat. The average fetal heart rate is between 110 and 160 beats per minute. It may change as the
fetus responds to conditions in the uterus. An abnormal fetal heart rate or pattern may mean that the
fetus is not getting enough oxygen or there are other problems. It also may mean that an emergency or
cesarean delivery is needed.
How is fetal monitoring done?
The most basic type of fetal heart rate monitor is to use a type of stethoscope called a fetoscope.
Another type of monitoring is with a hand-held Doppler device. This is often used during prenatal visits
to count the fetal heart rate. During labor, continuous electronic fetal monitoring is often used. The
specific details may vary slightly, but electronic fetal monitoring often follows this process:
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The healthcare provider puts gel on your abdomen to help the ultrasound transducer work
properly.
The provider attaches the ultrasound transducer to the abdomen with straps and sends the fetal
heartbeat to a recorder. The fetal heart rate is displayed on a screen and may be printed onto
special paper.
During contractions, a monitoring device (external tocodynamometer) is placed over the top of
the uterus with a belt. This device can record the patterns of contractions.
Sometimes, internal fetal monitoring is needed for a more accurate reading of the fetal heart rate. This
monitoring can be done when birth is close. Your amniotic sac must be broken and your cervix must be
partially dilated to do it. Internal fetal monitoring involves putting an electrode through the dilated
cervix. The electrode is attached to the scalp of the fetus.
What are a glucose challenge and a glucose tolerance tests?
The first 1-hour test is a glucose challenge test. If the results are abnormal, a glucose tolerance test is
done.
A glucose tolerance test is often done in weeks 24 to 28 of pregnancy. It measures levels of sugar
(glucose) in your blood. Abnormal glucose levels may be a sign of gestational diabetes.
How is a glucose tolerance test done?
The glucose tolerance test is done if you have an elevated 1-hour glucose challenge test.
The specific details may vary slightly, but a glucose tolerance test often follows this process:
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You may be asked to drink only water on the day you get the test.
The healthcare provider will draw a fasting sample of blood from a vein.
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You will be given a special glucose solution to drink.
The provider will draw blood several times over several hours to measure the glucose levels in your
body.
What is a group B strep culture?
Group B streptococcus (GBS) are bacteria found in the lower genital tract of about 1 in 4 women. GBS
infection often causes no problems in women before pregnancy. But it can cause serious illness in the
mother during pregnancy. GBS may cause chorioamnionitis. This is a severe infection of the placental
tissues. It can also cause postpartum infection. Urinary tract infections caused by GBS can lead to
preterm labor and birth, or pyelonephritis and sepsis.
GBS is the most common cause of life-threatening infections in newborns, including pneumonia and
meningitis. Newborn babies get the infection during pregnancy or from the mother's genital tract during
labor and birth.
The CDC advises that all pregnant women be screened for vaginal and rectal group B strep between 35
to 37 weeks gestation. If you have certain risk factors or a positive result, you should be treated with
antibiotics. This will lower the risk of passing GBS to your baby. Babies whose mothers get antibiotics for
a positive GBS test are 20 times less likely to develop the disease than those whose mothers don't get
treatment.
What is an ultrasound?
An ultrasound scan is a test that uses high-frequency sound waves to make pictures of the internal
organs. A screening ultrasound is sometimes done during a pregnancy to check normal fetal growth and
make sure of the due date. Ultrasounds may be done at various times throughout pregnancy for many
reasons.
In the first trimester
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To find out the due date. This is the most accurate way of finding the due date.
To find out the number of fetuses and see the placentas
To diagnose an ectopic pregnancy or miscarriage
To look at the uterus and other pelvic anatomy
In some cases to find fetal problems
Mid-trimester (sometimes called the 18- to 20-week scan)
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To confirm the due date. A due date set in the first trimester is rarely changed.
To find out the number of fetuses and look at the placentas
To help with prenatal tests such as an amniocentesis
To look at the fetal anatomy to see if there are any problems
To check the amount of amniotic fluid
To look at blood flow patterns
To watch fetal behavior and activity
To look at the placenta
To measure the length of the cervix
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To check fetal growth
Third trimester
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To check fetal growth
To check the amount of amniotic fluid
To complete a biophysical profile
To find out the position of a fetus
To check the placenta
How is an ultrasound scan done?
The specific details may vary slightly, but ultrasounds often follow the same process. Two types of
ultrasounds can be done during pregnancy:
Abdominal ultrasound. In an abdominal ultrasound, the healthcare provider puts gel on your abdomen.
The ultrasound transducer glides over the gel to create the image.
Transvaginal ultrasound. In a transvaginal ultrasound, the provider uses a smaller ultrasound
transducer. He or she puts the transducer into the vagina and rests it against the back of the vagina to
create an image. A transvaginal ultrasound makes a sharper image. It is often used in early pregnancy.
What are the risks and benefits of ultrasound?
Fetal ultrasound has no known risks other than mild discomfort. This is because of pressure from the
transducer on the abdomen or in the vagina. No radiation is used during the procedure.
Transvaginal ultrasound requires that the ultrasound transducer be covered in a plastic or latex sheath.
This may cause a reaction in women with a latex allergy.
Fetal ultrasound is sometimes offered in nonmedical settings to give keepsake images or videos for
parents. The ultrasound procedure itself is considered safe, but it's possible that untrained workers may
give parents false assurances about their baby's well-being. Or perhaps a problem may be missed.
Having ultrasound done by trained medical staff who can correctly understand findings is
recommended. Talk with your healthcare provider or midwife if you have questions.
What is genetic carrier screening?
Many genetic problems can be diagnosed before birth. Your healthcare provider or midwife may advise
genetic testing during the pregnancy if you or your partner have a family history of genetic disorders or
you have had a fetus or baby with a genetic problem.
Examples of genetic disorders that are commonly screened for include:
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Cystic fibrosis
Spinal muscular dystrophy
Fragile X
Thalassemia
Sickle cell anemia
Tay-Sachs disease
Diagnostic tests in pregnancy
Diagnostic tests are offered to women whose screening tests show:
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they have a higher chance of being a carrier for (or having) sickle cell or thalassaemia
a higher chance their baby may have either Down’s syndrome, Edwards’ syndrome, or Patau’s
syndrome
These tests can tell you for sure if your baby has any of these. It’s your choice whether you have the
diagnostic tests or not.
Your healthcare professional will talk it through with you and answer any questions you have. They'll
support you to make decisions that feel right for you.
The tests
There are 2 types of diagnostic tests: chorionic villus sampling (CVS) and amniocentesis.
Chorionic villus sampling (CVS)
CVS can be done from 11 weeks of pregnancy. It’s usually only offered in a specialist centre.
With the help of an ultrasound scan, a specialist doctor (obstetrician) will guide a fine needle through
your abdomen (tummy) and will take a small sample of tissue from the placenta. The placenta is inside
your womb. It links your blood to your baby and provides nourishment.
Chromosomes from the placenta can be counted from the sample. CVS does not give a clear result in
around 2 in every 100 samples. If this happens you may be offered a repeat test. Your obstetrician will
help you understand what your results mean.
Amniocentesis
Amniocentesis (you might hear it shortened to ‘amnio’) can be carried out after 15 weeks of pregnancy.
It usually takes about 10 minutes.
An ultrasound scan will check your baby’s position in the womb. The specialist doctor (obstetrician) will
guide a fine needle through your abdomen (tummy) into your womb. The doctor can then take a sample
of the fluid surrounding your baby (called amniotic fluid).
Your baby’s chromosomes can be counted from the sample.
Amniocentesis does not give a clear result in around 1 in every 100 samples. If this happens, you may be
offered a repeat test.
How safe are diagnostic tests?
CVS and amniocentesis aren't completely safe. There are some risks but they’re the only way to know
for sure if your baby has a condition. It’s your choice and healthcare professionals will support you
whatever you decide.
Around 1 in every 200 (0.5%) women who have a diagnostic test will miscarry as a result of the test. The
risk may be higher in twin pregnancies.
Are diagnostic tests painful?
Many women find the tests uncomfortable, sometimes painful.
Some discomfort in your lower abdomen for a couple of days is usual, and you can take paracetamol for
this. You should take things easy and avoid hard exercise for a day or two afterward.
What is gestational diabetes mellitus? Gestational diabetes mellitus (GDM) is a condition in which a
hormone made by the placenta prevents the body from using insulin effectively. Glucose builds up in the
blood instead of being absorbed by the cells.
Unlike type 1 diabetes, gestational diabetes is not caused by a lack of insulin, but by other hormones
produced during pregnancy that can make insulin less effective, a condition referred to as insulin
resistance. Gestational diabetic symptoms disappear following delivery.
What causes gestational diabetes in pregnancy? - Gestational diabetes occurs when your body can't
make enough insulin during your pregnancy. Insulin is a hormone made by your pancreas that acts like a
key to let blood sugar into the cells in your body for use as energy.
What happens if you have gestational diabetes when pregnant? - Diabetes that is not well controlled
causes the baby's blood sugar to be high. The baby is “overfed” and grows extra-large. Besides causing
discomfort to the woman during the last few months of pregnancy, an extra-large baby can lead to
problems during delivery for both the mother and the baby.
Possible complications for the baby
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Macrosomia. Macrosomia refers to a baby who is considerably larger than normal. All of the
nutrients the fetus receives come directly from the mother's blood. If the maternal blood has
too much glucose, the pancreas of the fetus senses the high glucose levels and produces more
insulin in an attempt to use this glucose. The fetus converts the extra glucose to fat. Even when
the mother has gestational diabetes, the fetus is able to produce all the insulin it needs. The
combination of high blood glucose levels from the mother and high insulin levels in the fetus
results in large deposits of fat which causes the fetus to grow excessively large.
Hypoglycemia. Hypoglycemia refers to low blood sugar in the baby immediately after delivery.
This problem occurs if the mother's blood sugar levels have been consistently high, causing the
fetus to have a high level of insulin in its circulation. After delivery, the baby continues to have a
high insulin level, but it no longer has the high level of sugar from its mother, resulting in the
newborn's blood sugar level becoming very low. The baby's blood sugar level is checked after
birth, and if the level is too low, it may be necessary to give the baby glucose intravenously.
Diabetes and Pregnancy
Pregnant woman with doctor getting her blood sugar checked.
Diabetes can cause problems during pregnancy for women and their developing babies. Poor control of
diabetes during pregnancy increases the chances for birth defects and other problems for the baby. It
can also cause serious complications for the woman. Proper health care before and during pregnancy
can help prevent birth defects and other health problems.
About Diabetes
Diabetes is a condition in which the body cannot use the sugars and starches (carbohydrates) it takes in
as food to make energy. The body either makes no insulin or too little insulin or cannot use the insulin it
makes to change those sugars and starches into energy. As a result, extra sugar builds up in the blood.
The three most common types of diabetes are:
Type 1
The pancreas makes no insulin or so little insulin that the body can’t use blood sugar for energy. Type 1
diabetes must be controlled with daily insulin.
Type 2
The body either makes too little insulin or can’t use the insulin it makes to use blood sugar for energy.
Sometimes type 2 diabetes can be controlled through eating a proper diet and exercising regularly.
Many people with type 2 diabetes have to take diabetes pills, insulin, or both.
Gestational
This is a type of diabetes that is first seen in a pregnant woman who did not have diabetes before she
was pregnant. Often gestational diabetes can be controlled through eating a healthy diet and exercising
regularly. Sometimes a woman with gestational diabetes must also take insulin. Every year, 2% to 10%
of pregnancies in the United States are affected by gestational diabetes.
For most women with gestational diabetes, the diabetes goes away soon after delivery. When it does
not go away, the diabetes is called type 2 diabetes. Even if the diabetes does go away after the baby is
born, half of all women who had gestational diabetes develop type 2 diabetes later. It’s important for a
woman who has had gestational diabetes to continue to exercise and eat a healthy diet after pregnancy
to prevent or delay getting type 2 diabetes. She should also remind her doctor to check her blood sugar
every 1 to 3 years.
Causes of Gestational Diabetes
Gestational diabetes occurs when your body can’t make enough insulin during your pregnancy. Insulin is
a hormone made by your pancreas that acts like a key to let blood sugar into the cells in your body for
use as energy. Learn more about Causes of Gestational Diabetes