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PREGNANCY RESOURCES
Prenatal Testing
by Mary Shanahan, RN,
CES and Pat DiGiacomo, RNC, MSN
Many different tests may be performed during the course of your pregnancy.
Some are routine, while others may be done based on your medical history,
family background, and race. All test results provide your caregiver with
important information which will help with the management of your pregnancy.
Your first prenatal visit answers a lot of questions for both you and
your caregiver. Information pertaining to your own health history is important
to help determine potential risk factors. Your initial appointment will
be longer than remaining office visits, and is likely to include the following:
Due Date Calculation
Your pregnancy is calculated to last approximately 40 weeks, or
280 days. A general estimation of when your baby is due is done as follows:
Add seven days to the first day of your last menstrual period, subtract
three months, add one year.
Blood Pressure
An increase in circulatory blood volume during pregnancy often affects
your blood pressure. It is important to determine a normal blood pressure
for you to use for comparison as your pregnancy progresses.
Breast Exam
A thorough exam of your breasts helps assess your ability to breastfeed
by checking for flat or inverted nipples, as well as screens for abnormalities.
Pelvic Exam
An internal exam will confirm your pregnancy, estimate the size and
shape of your pelvis and determine if the estimated due date is correct.
A PapTest, to screen for cervical cancer, will be done at
this time.
Weight Check
Most often, a recommended weight gain of 25-35 pounds is best, but
many predisposing factors will affect how much weight you gain. Your pre-pregnant
weight will be recorded, and your weight will be checked at each visit.
Be assured that eating a well balanced, healthy diet will result in the
right amount for you.
Urine Test
Testing of your urine provides information about your sugar and protein
levels, as well as detects possible infections.
Blood Tests
Blood tests provide a great deal of information. A thorough discussion
with your caregiver will determine which tests are right for you.
Routine Blood Tests - Routine laboratory tests, done
early in your prenatal care, determine your blood type, check for anemia
(lack of iron), sexually transmitted diseases, and Hepatitis B, as well
as determine whether or not you have had German measles or mumps. Your
caregiver may also recommend testing for HIV at this time.
Maternal Serum Screening Tests - These are blood tests
performed to find out whether a mother has a higher-than-average risk
of having a baby with certain birth defects.
Alpha-fetoprotein (AFP) - This protein is found in fetal
blood and amniotic fluid. A small amount of blood is taken from the
vein in the mother's arm between 15-18 weeks of pregnancy. The test
helps detect incidence of neural tube defects such as spina bifida,
and Down Syndrome. Results are usually available in 1-2 weeks. Only
a small number of patients whose maternal serum screening test show
abnormal levels have a baby with a birth defect. Abnormal tests results
are usually followed by additional diagnostic testing.
Multiple Marker Screening - This test measures levels
of hormones in the mother's blood, in addition to the AFP.
It is recommended for women over 35 years of age, and is used to screen
for Down Syndrome. Blood is drawn between 15-18 weeks of pregnancy,
and the results are available in 1-2 weeks. Abnormal test results are
usually followed by additional testing. Only 1-2% of women whose tests
show abnormal results actually have babies with Down Syndrome.
Additional tests may be recommended by your caregiver for identification
of genetic disorders or to check the well-being of your baby.
Ultrasound
Ultrasound is an important diagnostic tool that can provide valuable information
throughout your pregnancy about the health of your baby. It is the most
commonly used prenatal diagnostic procedure, and is often done between
16-18 weeks. A device is moved across the skin of the abdomen and high
frequency sound waves bounce off tissues inside the body. This creates
a picture of your baby on a television screen showing the skeleton and
organs, umbilical cord, and placenta. An ultrasound can determine many
things such as:
- age of the fetus
- growth progress of the fetus
- location of the placenta
- fetal position, movement, and breathing rate
- amount of amniotic fluid
- whether more than one fetus is present
- some birth defects
A Level II Ultrasound gives a more detailed evaluation
of the fetus. During the second half of your pregnancy, it can be used
to assess blood flow to the baby's heart and brain, as well as the uterine
and umbilical arteries.
Having an ultrasound may require some special preparation on your part.
If done early in pregnancy, you will need to have a full bladder at the
time of the test. Your caregiver will instruct you regarding the amount
of water you need to drink prior to the test.
Amniocentesis
This informative diagnostic test is usually done between 16-18 weeks of
pregnancy. It can be performed either in the doctor's office, or as an
outpatient hospital procedure. During amniocentesis, using sterile instruments
and the aid of ultrasound, a thin needle is guided through the abdomen.
A small sample of amniotic fluid is withdrawn from the amniotic sac and
sent to a lab to test for chromosomal abnormalities. Because amniocentesis
involves the study of chromosomes, your baby's sex can also be determined.
Results are available within 3 weeks from the time of the test. Complications
from this procedure are rare, but may include cramping, vaginal bleeding,
and leaking of amniotic fluid after the test. Later in pregnancy, amniocentesis
may be used to determine fetal lung maturity. In this instance, test results
are available within a few days.
Chorionic Villus Sampling (CVS)
Chorionic villi are tiny, fingerlike projections of tissue that make up
the placenta. CVS can be performed in the doctor's office or a hospital
setting. This test involves the removal of a small sample of tissue by
a catheter inserted through the vagina and cervix, or through a needle
inserted into the abdomen and placenta. The villi are sent to the lab,
grown in a culture and analyzed. CVS detects some of the same chromosome
problems as amniocentesis, but can be done earlier in pregnancy, usually
between 10-12 weeks. Results of CVS are available within 3 weeks. Risks
are rare, but the most common one is miscarriage. It is estimated that
1% of women who have CVS will have a miscarriage they would not have otherwise
had.
Monitoring the fetal heart rate and activity during pregnancy gives your
caregiver important information. Within weeks after your pregnancy has
been confirmed, your caregiver will listen to your baby's heartbeat at
each prenatal visit. This is done with a small device that transmits sound
waves through your abdomen, picking up the sound of your baby's heart.
The following tests use monitoring of your baby's activity level and heart
rate to determine how your baby is doing.
Kick Counts
Your caregiver may ask you to keep track of your fetus's movements or
kicks. This is a simple way to help determine fetal well-being during
the last trimester of your pregnancy. There are varying ways to do this
and your caregiver will tell you which way is best for you.
Non-stress Test
This test measures fetal heart rate in response to fetal movement. Usually,
a baby's heart rate increases as the baby moves. Changes in the heart
rate are considered a good sign. During this test, you lie in a comfortable
position with a monitor belt around your abdomen. Each time you feel the
baby move, you push a button which records on a strip of paper. Your caregiver
then evaluates your baby's movement in relation to your baby's activity.
The length of this test varies depending on how long it takes before the
baby is awake and active, but on average it takes 20-30 minutes to complete.
Contraction Stress Test
This test measures how the fetal heart rate reacts to the uterus when
it contracts. It is done to determine placental function and can take
up to two hours to complete. When the uterus contracts, there is a temporary
decrease of blood flow to the placenta. To perform this test, the mother
is either given a drug called oxytocin to make her uterus contract, or
she is told to rub one of her nipples lightly, which causes her body to
release oxytocin naturally. The response of the fetal heart rate in relation
to the contraction is recorded and evaluated by your caregiver. If the
placenta is working well, contractions do not cause a drop in fetal heart
rate, but if placental function is lessening, a drop in fetal heart rate
is seen. This is used to decide whether the baby should be delivered earlier
than the expected due date.
Biophysical Profile
This test combines electronic fetal monitoring with an ultrasound.
It is used to examine the fetal heart rate, muscle tone, body movement,
and the amount of amniotic fluid present. It also checks fetal breathing
movements. This is a simple test that can be repeated as necessary to
check the progress of your pregnancy.
Your own health history may never require many of the above mentioned
tests. Be assured that with proper communication between you and your
caregiver, only those tests best suited for your situation will be recommended.
This will help assure the ultimate goal for your pregnancy - healthy mom
and baby!
Editorial provided
by Mary Shanahan, RN, CES and Pat DiGiacomo, RNC, MSN. Both women are
perinatal education coordinators at North Penn Hospital in Lansdale, Pennsylvania.
| References:
• "Planning for Pregnancy, Birth, and Beyond",
2nd edition, American College of Obstetricians and Gynecologists,
Washington, D.C., 1995.
• Simpson, K.R. and Creehan, P.A., Association
of Women's Health, Obstetric and Neonatal Nurses, "Perinatal
Nursing", Lippincott-Raven, Philadelphia, PA, 1996.
• "Guidelines for Perinatal Care"
4th edition, American Academy of Pediatrics, American
College of Obstetricians and Gynecologists, Washington, D.C., 1997. |
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