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GENETIC TESTING
AMNIOCENTESIS
The most common type of genetic screening is done
using amniocentesis. In this procedure, a needle is inserted in a pregnant
woman's abdomen and a sample of amniotic fluid is taken. Fetal cells will
be present in the fluid (we are all just shedding cells all of the time,
just like animals shed hair - no wonder my house isn't clean!) and these
cells will be subjected to a chromosomal analysis. By looking at the chromosomes,
many disorders can be identified. The most commonly detected is Down syndrome,
which is also known as trisomy 21, because it is caused by having three
of the 21st chromosome. As mentioned in Appendix A in your text, the risk
of Down syndrome increases dramatically after age 35, which is a major
reason that many physicians encourage anyone over 35 to have an amniocentesis.
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If amniocentesis can identify disorders before birth, why doesn't everyone
have one?
There's the fact that these are not cheap. Mine cost around $650. The more
important reason, though, is that this is not a risk-free procedure. Think
about it, you are taking a large needle and inserting it into the stomach
of a pregnant woman. Does this sound like a bad idea to anyone besides
me? The risk of miscarriage is about 1 in 200.
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Why do people have an amniocentesis, then?
To be flat out honest with you, most people have them because they do not
want a child with a dability and are going to abort the fetus if it is
determined to be defective. Van der Zanden (1993) in his book Human Development
cites a study that examined 3,000 prenatal diagnoses and found that in
the 113 cases that an abnormal fetus was identified, 106 were aborted at
the parents' request. Incidentally, nothing is fool-proof. In these 3,000
cases, there were six where an incorrect diagnosis resulted in misleading
information to parents. The result was two health fetuses were aborted
and four fetuses with birth defects went undetected and were born. Six
out of 3,000 is not bad odds, but it is not zero.
MY AMNIOCENTESIS STORY
or
IT'S ALL DIFFERENT WHEN IT'S YOU
Okay, I am a well-educated
person, I have been teaching developmental psychology for years, including
the section on amniocentesis and genetic testing, which mentions the fact
that 94% of the time a fetus is identified as defective it is aborted.
Then, all of a sudden, at age 38, I find out that I am pregnant. This isn't
unwelcome news. After all, we had been talking about having a baby pretty
soon after we married. I had always wanted more children, but my husband
had been in a serious accident, which didn't make it seem like a good idea,
and then he had died, which sort of ended the possibility. My new husband
was 42, had never had children, and really wanted a baby. What could be
wrong?
Well, at 38, the chances
of having a child with a genetic defect, particularly Down syndrome, is
much higher than it is at 28 (when my last baby was born). I am the kind
of person who worries about everything that could possibly happen, so I
decided to have an amniocentesis because I knew that most of them come
out perfectly fine (96%, in fact) and it would greatly ease my mind over
the next few months to know that the baby was all right.
First, I had to sign a
consent form, and, on the form it said, "I have decided that I will have
an abortion if the baby has Down syndrome". Actually, I had decided no
such thing. The only possible explanation I could think of for this odd
requirement is that some group had opposed amniocentesis on the grounds
that it would encourage mothers to have abortions, so the lab and physician
had decided that a way to avoid this controversy was to only offer amniocentesis
to mothers who had already decided to have an abortion if the test results
were unfavorable. At that point, I hadn't made up my mind, but I figured,
what the heck, I would sign the paper. They couldn't MAKE me have an abortion
if I decided not to. Then I went home to wait for three weeks until the
amniocentesis was scheduled. (They really made sure I had time to
think it over. My friend, who was 42 when her second child was born, decided
not to have an amniocentesis because she said, "We were going to
have him no matter what, so there was no point.)
One of the things I was
not prepared for was how late in pregnancy an amniocentesis is performed.
Your textbook says that most physicans prefer to do an amniocentesis at
18-20 weeks. Then, it is another week to ten days before the test results
are available. Think about what that means. Quickening - the movements
of the fetus which are felt by the mother, begins early in the fifth month,
sometimes earlier. So, by the time you find
out if the fetus has some type of disorder, you have already felt the baby
moving inside of you for a week or two, sometimes more. Although the fetus
will not be able to survive outside the womb for another eight weeks or
so, this is not just a cluster of cells. The fetus is about ten inches
long and weighs around a pound. All of the organs have developed, internally
and externally, right down to the fingernails and toenails.
By the date of the appointment,
I still had not decided what to do. My husband said, "You know, if we have a baby who is severely
handicapped, we probably won't be able to have another baby. Four kids
is hard enough, but when one of them requires a lot of extra time and money,
it just seems like it would be too much to have a fifth one. I really would
like to have one healthy, normal baby."
My oldest daughter, who is fifteen, also gave
her own, unsolicited opinion, one day,
"You want to hear my opinion? Well, you're
going to anyway. The way I figure it, you two are going to die sooner or
later because you are old, let's face it. You're almost 40 and Dennis is
over 40. So if you have a handicapped baby that can't take care of itself,
I am going to end up taking care of it. This may seem like an awful thing
to say, but when I am 35, I want to be raising my own kids, not some handicapped
kid that you had. I mean, if Ronda or Jenn (her younger sisters) got hit
by a truck and got brain damage, I would take care of them. But, I think
it is pretty selfish of you to have a baby that you know someone else will
have to end up taking care of.
One of the things they don't tell you about amniocentesis
is that it hurts, not nearly as much as having a baby, but it hurts nonetheless.
What do you expect, really, when some person jabs a long needle into your
stomach? The obstetrician said, "It shouldn't hurt, it must be because
you are so thin." My friend, who is somewhat overweight, was told by her
physician "Oh, it's not supposed to hurt, it must be because you are so
heavy." It hurts.
So, then, we were told,
it would be 7-10 days before we got the results back. Personally, I thought
it was very important to decide whether or not we were going to keep the
baby BEFORE we knew. I don't know why I thought that, maybe just because,
if she ever asked me "Mom, would you have had me no matter what?"
I could answer, "yes".
In the end, that is what
I decided, regardless of anyone else's opinion. As I told my other children,
"I took what I got when the three of you were born, and I just can't see
saying with this baby, 'If it's not perfect, just kill it!' "
So, we, or rather, I decided to have the baby.
Then, of course, there were still several more days until we found out
the test results. I was beyond nervous. I called the doctor's office every
day. FINALLY, nine days after the test, I received a call from the obstetrician.
He just wanted me to know that everything was fine. We were having a little
girl, and every test had turned out fine.
An ultrasound is a much less precise measure
than an amniocentesis, with no risk for the fetus. Sound waves are bounced
off the fetus, just like the sonar used by submarines is used to 'see'
the shape and size of objects under water. The shape and size of the fetus
can be seen, and any obvious malformations, such as missing limbs. Ultrasonography
also detects multiple fetuses. This is how Bobbi McCaughey found out she
was going to have septuplets. While it was common when I had my older children,
for women to be carrying twins, or even triplets, and not have any idea
until the actual birth, this is seldom the case any more, at least among
women who receive prenatal care.
When I had my last baby, eleven years ago, ultrasound
was only used in the case of suspected problems. These are now used routinely.
In fact, living on the yuppie westside of Los Angeles county, there is
even a physician who advertises that he will schedule sonograms on weekends
and give a you a video and photographs of the fetus (for a large fee, of
course). Sort of like your first baby pictures. As your textbook mentions,
this ability to see the fetus before birth may facilitate parental bonding.
We had a sonogram a couple of days after the amniocentesis results came
back. My husband and two daughters came to watch. We could see her moving
around, see her arms, head, hands, legs, and see her jump when my youngest
daughter leaned close to my stomach and yelled, "Hey, anybody in there?"
Response to loud noises is innate (loud noise is an unconditioned stimulus,
if you remember your classical conditioning theory). Yes, we did get pictures,
which my husband took to scan into the computer so he could put them on
his home page for relatives around the country to see what our baby looked
like. (Like any other sonogram at four and a half months, I would imagine).
What struck me as rather eerie about the whole thing was that, if the tests
had turned out abnormal, most people would have had an abortion scheduled
for this day. Strange, isn't it? While this may sound as if I am saying people who
have an abortion following an amniocentesis are heartless, I really don't
think that. Raising any child is an extremely difficulty task. Raising
a child who is disabled is even harder. A woman I interviewed for a research
project commented on her experience having a severely disabled child, "People
say God must have picked you specially to cope with the challenges of this
child. #$%^! No one wishes and prays for a handicapped baby when they are
pregnant. No one."
All I am saying is, it is one issue when you discuss
genetic testing and the decision to have an abortion as a hypothetical
issue, and a whole different story when it is you.
FTHE
WORLD WIDE WEB EQUIVALENT OF A FIELD TRIP E
Click below to go to a really cool site on genetics. Before you do,
I might mention that the pictures on the web pages sometimes take
forever to show up, so you may want to wait or just read the stories and
go on. Be sure you at least read the one entitled "Genes of Life
and Death", as well as any others that strike you as interesting. ALSO,
you need Java and a plug-in called shockwave installed on your computer
if you are going to view the animated sections. If you don't have these
(or don't know if you do), don't worry about it. The animations are kind
of fun to look at but not at all essential to understanding the information.
You click on the pictures to make things happen in the animation. (If you
click on 'done' or 'next ' in the "Cytoplasmic Cell Donation", it will
show you what happens next. If you click on specific body parts in "The
Manmade Man", it will zoom in to show more detailed information on that
body part. Since these pages weer developed by the Public Broadcasting
System, there is not a link back to this page, so you will have to click
on the back arrow in the top left of your screen to get back here.
All right, already,
click here and go to the innovations web site. Click here to learn all about the graphic details
of pregnancy and birth.
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