[Gnumed-devel] address@hidden: Gestational age [was: Re: Age and named quantities]]

[Karsten Hilbert]

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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