From: larrabee@cse.ucsc.edu (Tracy Larrabee)
Newsgroups: misc.kids
Subject: Ultrasound excerpts from book on prenatal tests
Date: 3 Sep 1992 18:40:02 GMT
Organization: University of California, Santa Cruz (CE/CIS Boards)
Distribution: world
NNTP-Posting-Host: arapaho.ucsc.edu


I just got back the book I recommended, "What Tests for my Unborn
Baby" (Authored by de Crespgny and Dredge, 1991), and I want to
include a couple of paragraphs from the book on recent misc.kids threads:

   The Examination

   The most vivid memories many women have of the scan is of an
   agonizingly full bladder.  Fortunately this is now rarely necessary.
   An overfull bladder is in fact counterproductive, usually resulting in
   poor pictures.  Check what your doctor wants you to drink.  Often a
   little urine in your bladder is preferred but sometimes a totally
   empty one is best.

   The logic of a full bladder was that it lifts the uterus out of your
   pelvis, sometimes making it easier to see through the abdomen.  It
   also pushes the bowel away from the front of the uterus.  As bowel
   also contains air through which ultrasound will not pass, its presence
   results in poor images.  Moder equipment allows the doctor to obtain
   good views without a full bladder by angling a small transducer
   through a part of the abdomen where intestines are not in the way.

and on another topic:

   Can Ultrasound damage your Baby?

   [Summary where they say that hundreds of studies say it is safe followed
   by:]

   Research into the effects of ultrasound includes laboratory studies of
   cell changes, animal research, and follow-up studies of babies exposed
   to ultrasound.  In each case no reproducible ill effects have been
   shown to result.  A well-designed study reported in 1984 involved 452
   babies who underwent ultrasound examination prior to birth and 381
   matched controls, babies of similar background who were not scanned.
   Physical development and tests of nerve function were compared at
   birth and again between seven and twelve years, revealing no
   significant differences.

   One of the most widely publicized adverse reports was of changes in
   the chromosomes of cells exposed to ultrasound.  This report has not
   been confirmed by other workers using hte same methods, so it is
   believed that the reported chromosome changes must have been caused by
   some other agent.  While there has been criticism of the construction
   of some studies, the sheer number showing no ill effect has reassured
   physicists, obstetricians and radiologists that ultrasound
   examinations are safe.  Confidence in its safety has reached such a
   level that it has become a routine procedure in pregnancy in many
   countries.  Indeed, in Germany the law demands that every pregnant
   woman must be offered two ultrasound examinations by her doctor -- one
   early in pregnancy and one late.

   There are several factors which reduce the possibility of harm from
   ultrasound.  When examining a pregnancy, low power levels are used.
   In the previous section we explained that ultrasound uses extremely
   short pulses of sound, so that the transducer is only sending out
   sound waves for approximately one thousandth of the examination time.
   You will also see only part of your baby on the screen at one time, so
   the rest of it is receiving minimal ultrasound exposure.  Thus any one
   part of the baby receives ultrasound for a very short time during
   examination.

   It has been known for a long time that ultrasound at much higher power
   levels than is used for diagnosis can produce cell damage.  These high
   power levels have been used for the treatment of cancer and by
   physiotherapists to treat muscle injuries.  They should not be
   directed at the abdomen of a pregnant woman.

   Despite its safety record, ultrasound should not be used
   unneccessarily; it is recommended for clinical benefit only.  Most
   people would feel that to have an ultrasound examination merely to
   find out the sex of the baby would be frivolous.  If, however, a scan
   is being carried out for some other reason then it takes little extra
   time to look at the sex if that is the parents' wish.

   Neither you nor your baby will notice any sensation from your
   ultrasound examination.  In particular, the scan does not make you
   feel warm.  As you do not feel anything, and you receive more power
   than your baby since the ultrasound must pass through your tissues
   first, your baby also cannot feel anything.  Ultrasound cannot make
   your baby move.  Any movements observed during the examination are
   those that would have occurred naturally.  There has also never een
   any evidence to support the suggestion that ultrasound can damage your
   baby's hearing.


--
Tracy Larrabee		larrabee@cse.ucsc.edu