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2a. What disabilities can be detected by these tests?


This article is from the Pregnancy Screening FAQ, by Lynn Gazis-Sax (gazissax@netcom.com) with numerous contributions by others.

2a. What disabilities can be detected by these tests?

From Robbrenner@aol.com (Robert Brenner MD):

2a. There are too numerous birth defects to list. In general prenatal
testing can pick up all chromosomal abnormalities, many structural
abnormalities, and many metabolic abnormalities.

Two of the most common disabilities which are tested for are Down
Syndrome and neural tube defects. Some information on these follows.

Neural tube defects are one of the leading disabilities among
newborns. The main neural tube defects are anencephaly and spina
bifida. Infants with anencephaly are born with a malformed brain and
skull; they are stillborn or die shortly after birth. Spina Bifida
occurs when the spinal cord does not completely close. Until the
1960's, many newborns died of hydrocephalus. Now 80-95% survive to
adulthood. The degree of disability varies depending on how severely
the spinal cord has been affected and where on the spinal cord the
problem occurs. It may involve a slight limp, or paralysis and use of
a wheelchair. People with spina bifida may be incontinent, and some
have kidney and urinary tract problems. Intelligence is not affected
unless the complication of hydrocephalus is present. If hydrocephalus
is present, intelligence may be either impaired or normal, depending
on the degree of hydrocephalus, and the success of surgical

Neural tube defects are influenced both by genetics and by the
environment. There is a lot of geographic variation in frequency, with
incidence in the United Kingdom several times that in the Unites States.
In the United Kingdom, incidence is highest in northern Ireland and
lowest in southern England. The frequency of neural tube defects is
*reduced* by taking folic acid during pregnancy (women planning to be
pregnant should start this before pregnancy, so as to be taking it during
the time when they do not yet know they are pregnant). Spina bifida may
be ameliorated by delivery by a scheduled C-section (see below).

From Trish Jalbert (tjalbert@best.com):

In a nutshell, Down Syndrome is the presence of three 21st chromosomes.
There are actually three types of Down Syndrome, the most common
being Trisomy 21 which is simply the presence of the pesky extra
chromosome tacked on to the other two (95% of cases). In
Translocational DS the extra chromosome is translocated, or stuck on
to, one of the other chromosomes (3 to 4%). In Mosaicism, the person
has the extra chromosome in only some of his or her cells (1%). It
is important to find out which type of DS someone has, since
Translocational DS is hereditary. The parents can be carriers
without showing any signs of Down Syndrome themselves. One really
important fact for us guilt-machine moms is that new research shows
that in 70 to 80% of the time, it is the egg that contributes the
extra 21st and the rest of the time it's the sperm. (Sperm with
problems just aren't very hearty , I have been told.) So it's not
always the mom!

There are numerous effects. Some 12% of babies with Down Syndrome
have gastrointestinal defects, and some 40% have heart defects. Both
of these types of defects are correctable with surgery, although it
is scary to have your baby have such a problem. DS kids also seem to
have a susceptibility to infections. There can be hearing problems,
thyroid problems and a few other things. DS babies also tend to have
low muscle tone, which means that they may learn to crawl, walk and
such like later than their regular peers. Most everyone is aware of
the cognitive delays. Although I don't particularly like to judge
anybody by their IQ score, DS people tend to have IQ's from 40 to 70,
which counts as moderate to mild impairment. Some people score
higher, some lower.

I cannot stress enough, however, that DS babies, children and adults
are more like their relatives and like the rest of us than they are
My daughter looks *just like* my husband. (It's actually rather eerie.)
Many people seem to have heard of the stereotype of DS kids as being
extremely loving people. While no stereotype accurately represents a
person, I think every one is hitting on the fact that DS kids do
develop quite well socially. This is *not* like parenting a child
who is autistic. My daughter, who was extremely ill at birth due to
meconium aspiration as well as a heart defect, recognized my husband
and me very early on and acted much differently when we were at the
hospital visiting her. (she spent 7 weeks in intensive care at
birth.) My husband and I have a joke about things like this. We
like to say "You know, DS kids usually don't (fill in blank)." The
reality now is that we *don't know* the potential of today's babies
born with DS. Children with DS have only recently been offered
adequate schooling and in the past were also sometimes denied the
love of their families, since many were sent to live in institutions.
Kids and adults with DS are now astonishing us all. Remember Chris
Burke on "Life Goes On?"

Yes, babies with DS probably take extra work. Although a large
number of them are perfectly healthy, a lot of parents do have major
medical problems to deal with. When that is done, there is early
intervention to think about, then school. Many kids with DS are now
being fully included in regular classrooms, although that option is
not for all families. Many adults can live is supported environments
on their own- parents will not always have to care for their DS

For me, all of the hassle has been worth it- I already cannot imagine
my life without Miranda, who is now 3 months old. She is a very
sweet baby- even unbiased people think so, so it must be true! ;-)
And I am writing this on the eve of her heart surgery, something that
would task any parent's coping. It still has all been worth it.

[Note from LG: Miranda died during that heart surgery. Trish would like
me to reassure people that what happened to Miranda was rare, rare enough
that a paper is being written about her. Trish is still willing to answer
people's emailed questions about Down Syndrome.]



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