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[Gnumed-devel] address@hidden: Gestational age [was: Re: Age and named q
From: |
Karsten Hilbert |
Subject: |
[Gnumed-devel] address@hidden: Gestational age [was: Re: Age and named quantities]] |
Date: |
Fri, 25 Feb 2005 09:13:43 +0100 |
User-agent: |
Mutt/1.3.22.1i |
more to keep
----- Forwarded message from USM Bish <address@hidden> -----
>
> On Thu, Feb 24, 2005 at 01:21:05PM +0000, rob challen wrote:
> > Sorry to add my thoughts after the discussion has died down.
> >
>
> Actually, yours is the first concrete proposal towards the
> issue of gestational age ... so cant't really say that the
> discussions have died really ;-)
>
> >
> [lots snipped]
> >
> > The two most useful numbers to the neonatologist and
> > paediatrician are therefore Chronological Age (from D.o.b) and
> > Corrected Gestational Age, all the rest can be worked out if
> > you know todays date.
> >
> > o DOB = Today - Chronological Age
> > o Gestation at birth = CGA - Chronological Age
> > o Est date delivery = Today - CGA + 40*7
> > o Est date of conception (rarely used in medicine) = Today - CGA + 15***
> >
>
> Three of the above 4 computations are CGA based, whereas CGA
> itself remains uncertain (being based on gestation). Do we base
> gestation on something like this ?
>
> if ( ultrasound done in 12 to 16 weeks ) {
> gestation = ultrasound_gestation
> confidence = (+/-) 2 days
> } else {
> gestation = ($today - $LMP) + 14
> confidence = (+/-) 3 days
> }
>
> >
> > Given the uncertain nature of life I think it is eminently
> > sensible to record a confidence interval for CGA, as was
> > previously suggested.
> >
>
> Does the above convey what you want to say ?
>
>
> Dr USM Bish
> Bangalore
>
>
> PS: I have some reservations on the EDD estimation, because the 40
> week rule of thumb (Nagele's Rule) is not supported by current
> statistics. Gestation is not a fixed period and affected by
> factors like parity and ethnicity. However it is not of much
> relevance to gestational age, per se.
>
> -
> If you have any questions about using this list,
> please send a message to address@hidden
----- End forwarded message -----
----- Forwarded message from rob challen <address@hidden> -----
> X-Mailer: Microsoft Outlook, Build 10.0.6626
>
> Yes.. I later though after sending the e-mail that what I'd meant to say
> was, of course, that the two most useful numbers are indeed CGA and
> Chronological age but they are of course both variable depending on the
> current date (one gets older every day, after all...).
>
> Equivalent fixed values that do not change are of course Date of Birth and
> Gestation at birth. These are the numbers you actually need to record. The
> rest change every day.
>
> Your calculation of gestation below is right if '$today' is the child's
> birthday. It's probably better to express it as:
>
> if ( ultrasound done in 12 to 16 weeks ) {
>
> //EDD by scan method for calculating gestation
> $gestation_at_birth = ($ultrasound_EDD - $date_of_birth)/7 + 40
> confidence = (+/-) 2 days
>
> } else {
>
> //EDD by dates method for calculating gestation
> $gestation_at_birth = ($date_of_birth - $LMP) + 14
> confidence = (+/-) ???3 (???maybe 7) days
> }
>
> Gestation (at birth) is after all a constant value, just sometimes not a
> very accurate one, and sometimes subject to revision.
>
> The confidence interval of the the EDD by dates method is probably quite
> large - I wouldn't even like to hazard a guess. EDD by dates is frequently
> quite wrong though. EDD by scan is better, but by no means foolproof.
>
> Usually the question "how sure are you about your dates" is asked of the
> mother at some stage and the response is sometimes recorded in the notes.
> It's not very scientific. Infants who initially are thought to be 32 weeks
> gestation are sometimes 'down-graded' to 34 weeks gestation based on their
> physical signs or dubowitz score, for example.
>
> In the end though it is about setting a time. In the grand scheme of things
> gestational age is only ever a guess. It is worth recording, but I know of
> infants that have lost or gained a couple of days over a long stay in NICU
> from administrative error without any major consequences. So it probably
> isn't worth losing sleep over.
>
> Rob.
>
>
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On Behalf Of USM Bish
> Sent: 24 February 2005 18:55
> To: address@hidden
> Subject: Gestational age [was: Re: Age and named quantities]
>
>
> On Thu, Feb 24, 2005 at 01:21:05PM +0000, rob challen wrote:
> > Sorry to add my thoughts after the discussion has died down.
> >
>
> Actually, yours is the first concrete proposal towards the issue of
> gestational age ... so cant't really say that the discussions have died
> really ;-)
>
> >
> [lots snipped]
> >
> > The two most useful numbers to the neonatologist and
> > paediatrician are therefore Chronological Age (from D.o.b) and
> > Corrected Gestational Age, all the rest can be worked out if you
> > know todays date.
> >
> > o DOB = Today - Chronological Age
> > o Gestation at birth = CGA - Chronological Age
> > o Est date delivery = Today - CGA + 40*7
> > o Est date of conception (rarely used in medicine) = Today - CGA +
> > 15***
> >
>
> Three of the above 4 computations are CGA based, whereas CGA itself
> remains uncertain (being based on gestation). Do we base gestation on
> something like this ?
>
> if ( ultrasound done in 12 to 16 weeks ) {
> gestation = ultrasound_gestation
> confidence = (+/-) 2 days
> } else {
> gestation = ($today - $LMP) + 14
> confidence = (+/-) 3 days
> }
>
> >
> > Given the uncertain nature of life I think it is eminently
> > sensible to record a confidence interval for CGA, as was
> > previously suggested.
> >
>
> Does the above convey what you want to say ?
>
>
> Dr USM Bish
> Bangalore
>
>
> PS: I have some reservations on the EDD estimation, because the 40
> week rule of thumb (Nagele's Rule) is not supported by current
> statistics. Gestation is not a fixed period and affected by
> factors like parity and ethnicity. However it is not of much
> relevance to gestational age, per se.
>
> -
> If you have any questions about using this list,
> please send a message to address@hidden
>
>
>
> -
> If you have any questions about using this list,
> please send a message to address@hidden
----- End forwarded message -----
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