[tri-med] Genetics 105 - Risks Based on Age

Cheryl asked whether the statistics for increased risk based on the mothers
age of the occurrence of Trisomy were "outdated" and if anyone kept track of
the statistics.

The statistics unfortunately are fairly accurate.

They are generally based on the results of two studies. One by Cuckle, Wald
and Thompson (1987) and published in the British Journal of Obstetrics and
Gynecology (Volume 94 pp 387-402)
This study looks at the chance of having a live-born baby with Down Syndrome
based on maternal age. (as I said previously the risk based on increased
paternal age does not seem to rise)

These are the statistics that are also used for T-18. They really are about
the same.

The other stats that are used are those collected in a study by EB Hook
(1981) published in the Journal of Obstetrics and Gynecology (Volume 58 pp
282-285). This study gives the chance of having a liveborn baby with any
chromosomal abnormality.

I will give the statistics in a bit. But as for reliability they check out
with the Australian figures....... In Australia every chromosomal
abnormality diagnosed in the first 12 months of life are mandatarily
reported to a federal organisation. These are then compiled and published in
understandable form :-)) eg age of mother, diagnosis, whether the pregnancy
was terminated etc

I have looked and scrutinised the Australian statistcs and they do bear out.
So sadly I must agree that the figures we are quoted are true. And yes I was
in the AMA (advanced maternal age) range when I had Alex....... I was 36,
and I never even thought of that ge being at increased risk......... and
sadly wasn't even told!!

It does seem however just by looking at the people we come in contact with
are in the younger age range. There are two reasons for that. People under
35 have more babies than people over over 35 so the actual number of babies
out there to younger mums is higher, but if you take the number of babies
actually born and divide that by the number of babies with a "problem" then
the risks are higher the older we get.

The second reason is that doctors are very aware of the risks in older
mothers and therefore they screen more carefully and are more likely to do
more tests to check.

The third reason is that, despite a change in trend, most pregnancies
diagnosed with a chromosomal abnormality prenatally are terminated. This is
even more so in the case of older parents because they know that they will
in fact be "elderly" parents caring for a disabled child and fear that they
will not be able to cope..........

Now I don't raise those points to cause a debate on the pro's and con's of
termination, I am simply stating fact........ Remember we must respect every
individuals right to make their own choices whether we agree or not!!!!

Now those statistics are:
Mothers Age is at the expected date of delivery and is the first column
(this is hard to type a table in an e-mail!!). The second column is the
chance of having a live-born child with Down Syndrome and the third column
is the chance of having a live-born child with any chromosomal abnormality

Age              T-21               Chrom
35                1:384                1:179
36                1:307                1:149
37                1:242                1:124
38                1:189                1:105
39                1:146                1:81
40                1:112                1:64
41                1:85                   1:49
42                1:65                    1:39
43                1:49                    1:31
44                1:37                    1:24
45                1:28                    1:19

so even at 45 you CAN still have a baby with no problems and some people
do - its just that the odds certainly aren't in your favour........


                  Building ___ooOOoo__ Rainbows
                       www.trisomyonline.org
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