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From: naomi@ubc-medg (Naomi Altman)
Newsgroups: net.women
Subject: Re: Amniocentesis
Message-ID: <128@ubc-medg.UUCP>
Date: Tue, 6-Sep-83 20:15:51 EDT
Article-I.D.: ubc-medg.128
Posted: Tue Sep  6 20:15:51 1983
Date-Received: Wed, 7-Sep-83 10:11:10 EDT
Lines: 45

Well, I'm not a geneticist or a doctor, but I work in the department of 
medical genetics.  I just consulted with a professor in the department whose
specialty is genetic counselling.  She handed me a stack of papers on 
amniocentesis - complications of pregnancy, post-natal complications, and
legal aspects for doctors involved in counselling.
  Estimates of the incidence of Downs' syndrome in women over 35 range 
from 2% to 4%.  In 1978, 80 types of genetic problems could be identified
with amniocentesis.  The number has grown since then.
  All of the reports I read indicated no differences in birth complications
or in post-natal development for babies that had been subject to 
amniocentesis, and babies of mothers of similar age who had not.  
The spontaneous abortion rate after amniocentesis was, in all studies, very
similar to the rate in mothers of similar age who had not undergone amnio -
however, all the reports estimated additional risk of 1% or less (i. e. they
erred on the side of caution.)  
  The most comprehensive study I have was done in Canada in 1977. (And things
have improved since then.)  In 1227 amnio cases, the spontaneous abortion rate
was .2% (this is *extremely* low) and there were mild maternal complications
(such as vaginal leakage) in 3.4% of the cases.  There were 7 misdiagnoses in
1227 amnios - of these 2 were wrong sex, and one was a fetus that was already
dead in the womb.  2 normal pregnancies were terminated due to these 
misclassifications.  As well, two normal pregnancies (one of which was twins)
miscarried due to compications. A 1979 study of 3000 amnios done in the 
U.S. had 14 misclassifications, of which 8 were wrong sex.
  These two studies also found that larger needle size was implicated with
increased risk of complication.  Larger needles are used in order to get a
large enough sample of fluid to analyse.  They found that taking 2 samples
with a smaller needle was preferable.
  My informant expressed the view that with ultrasound, there was negligible
chance of deforming the fetus with the needle.  The literature cites two
cases (out of thousands of amnios).  One author felt that ultrasound was
not useful in avoiding this problem.  Evidence suggests that ultra-sound 
poses no risk to mother or fetus.
  A note in the New England Journal of Medicine, 1980 entitled "The Pro-life
bonus of amniocentesis" reports on a survey of 297 mothers who had 
undergone amniocentesis.  I quote: 
 "Without the reassurance that amniocentesis would provide, 8.4% of these
pregnancies would not have been undertaken, and another 4.0% would have been
aborted. During the five-year period, positive diagnoses have led to 
therapeutic abortions in 7 cases (approximately 2%). There is, therefore,
an apparent "bonus" of 10 pregnancies per 100 that might not have been
completed is amniocentesis had been unavailable to this group of women. "

                    Naomi Altman
                    !decvax!microsoft!uw-beaver!ubc-vision!ubc-medgen!naomi