Prenatal tests are important for your health and your unborn baby's health. Here's what to expect.
"Taking good care of yourself during pregnancy is the most
important way to have a healthy baby," says E. Charles Lampley, MD,
assistant professor at the Chicago Medical School and an ob-gyn at Mount Sinai
Hospital in Chicago.
There are a number of prenatal tests you'll go through while
you're pregnant, but the very first test you'll take is the one that will tell
you whether you're actually pregnant in the first place. "To get off to a
healthy start, it is important to know that you are going to have a baby as
early into the pregnancy as possible," Lampley says. If you have regular
periods and you miss one, that's a pretty good sign (although not a foolproof
one). Another indication, he says, is simply whether you think you're pregnant.
"It's a life-altering event, and the psychological part can clue you
in."
If you do think you're pregnant, have your hunch confirmed
through a blood test at your doctor's office or a health clinic, Lampley says.
You can use a drugstore test first, but he cautions that these are only about
75% accurate. Tests performed at the doctor's office are almost 100%
accurate.
Once you know for certain that you're pregnant, schedule
regular appointments -- even if you're feeling fine. "Unless there are risk
factors, you should see your obstetrician once a month for the first 28 to 32
weeks," Lampley says. "Women who develop diabetes or high blood
pressure during pregnancy, or who have a history of delivery before 37 weeks,
should see the doctor more often."
According to Boris Petrikovsky, MD, PhD, chairman of the
department of obstetrics and gynecology at Nassau University Medical Center in
East Meadow, N.Y., and author of What Your Unborn Baby Wants You to
Know, your first prenatal visit will include blood tests to determine your
blood type; your iron level to see if you're anemic; your blood glucose level
to check for diabetes; and your Rh factor (if your blood is Rh negative, and
the father's is Rh positive, the fetus may inherit the father's Rh-positive
blood, which could cause your body to make antibodies that would hurt your
unborn child). You will also be tested for HIV, hepatitis B, and syphilis, as
well as whether you're immune to rubella (German measles), since coming down
with this illness while pregnant, especially in the first three months, can
cause birth defects.
A Pap smear -- if one has not been performed recently -- will
be done to test for early cervical cancer and sexually transmitted diseases
such as chlamydia and gonorrhea, while a urine specimen will be taken to check
for urinary tract infections. A blood pressure check will also screen for high
blood pressure, which can interfere with the blood supply to the placenta.
These tests are all routine and are performed on every pregnant
woman, Petrikovsky says.
The next set of prenatal tests will be performed between weeks
8-18 of the pregnancy, Petrikovsky says, and will include an ultrasound
screening, which can help determine your due date more accurately, and also
look for abnormalities in the fetus. During this time, your doctor will also
take other blood tests (known as a triple screen or a quad screen) that will
measure blood levels of alpha-fetoprotein, estriol, hCG (human chorionic
gonadotropin), and inhibin, which can indicate whether the fetus is at risk for
abnormalities such as Down syndrome or spina bifida. A newer blood test, PAPPA
(pregnancy-associated plasma protein A), conducted during weeks 10-14 of the
pregnancy and used in conjunction with an ultrasound screening, is a good
choice for women who are at risk of having a baby with a chromosomal
abnormality, says Petrikovsky.
Depending on the results of the blood tests, the age of the
mother (ages 35 and above), or the family history of the mother-to-be, the
doctor may then suggest further prenatal tests, such as chorionic villus
sampling (CVS) or amniocentesis, both of which detect Down syndrome or other
abnormalities. CVS, which is usually done between weeks 10-12 of the pregnancy,
can be performed either by passing a thin tube from the vagina into the cervix
to remove a sample of tissue from the chorionic villi (which makes up the
placenta), or by inserting a needle through the abdominal wall to obtain a
tissue sample. Amniocentesis, which is performed between weeks 16-18 of the
pregnancy, involves the insertion of a needle through the abdominal wall into
the uterus, removing some of the amniotic fluid. Both CVS and amniocentesis
carry a small risk of miscarriage.
Between weeks 24-28, you will be screened again for diabetes
(some women develop pregnancy-related diabetes, known as gestational diabetes,
which usually clears up after the baby is born), and patients who are Rh
negative will be checked for Rh antibodies (which can be treated through a
series of injections), says Petrikovsky.
At the end of the pregnancy, between weeks 32-36, you may be
retested for syphilis and gonorrhea, as well as for group B strep (GBS), a type
of bacterium that can cause meningitis or blood infections in newborn infants;
if you test positive for GBS, you will be given antibiotics during labor and
delivery to minimize the risk of transmitting the bacterium to your infant.
Though these are all routine tests, there may be other prenatal
tests that your obstetrician will recommend, depending on your racial or ethnic
background or family medical history, says Vivian Weinblatt, MS, CGC, regional
manager of genetic services for Genzyme Genetics in Philadelphia and former
president of the National Society of Genetic Counselors.
Certain populations, for example, are at risk for certain
diseases, Weinblatt explains. Ashkenazic Jews (those of Eastern European
descent) as well as French Canadians and Cajuns are at high risk for Tay-Sachs,
a debilitating neurological disease that usually results in a child's early
death. Since the increased use of screening tests to determine whether
parents-to-be are carriers of Tay-Sachs became more prevalent in the 1970s, the
incidence of the disease has dropped dramatically, says Weinblatt.
Weinblatt says other illnesses that are specific to the Jewish
population and can be screened with a blood test or tissue sample are Canavan
disease; mucolipidosis type 4; Niemann-Pick disease type A; Fanconi anemia type
C; Bloom syndrome; familial dysautonomia; and Gaucher disease.
Africans, African Americans, Southern Europeans, and Asians are
at higher risk for blood-related illnesses such as sickle cell anemia and
thalassemia, says Weinblatt.
If you have a family history of illnesses such as muscular
dystrophy, hemophilia, or cystic fibrosis, you may also want to consult a
genetic counselor, Weinblatt advises. "A genetic counselor can't treat you
or your unborn child, but he or she can let you know how your risk factors can
affect your pregnancy.
"When you know ahead of time -- even if you find out that
both you and your partner are carriers of a specific illness -- you can prepare
yourself emotionally, you can find the proper doctor, etc. You'll have a
greater feeling of control when you know what to look for."
However many prenatal tests you have, try not to become too
anxious. Remember, says Lampley, that "the vast majority of unborn children
are perfectly normal, provided the mother has taken care of herself and her
child."
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