ABC of FGR : Can we make mistakes and
over treat a normally growing foetus??
Opinion & clinical experiences of the
members:- We
have never asked ourselves why
How
accurate is USG in picking up FGR in pregnancies which are well dated?? Exciting developments
Ans:- Even if all the parameters are used then also there can be missing of some FGR fetuses.
Limitations ore
fallacies of USG as a means of diagnosing FGR!!!
Ans:- Not only missing some cases of FGR by USG it is equally possible that ,even if all the measurements are used then too there is a possibility that 15-75 % of
normal fetuses will exhibit
abnormal USG parameters and will be considered as FGR
? The role of
USG , Doppler in particularly in the diagnosis / prediction of FGR. Definition: Intra
uterine growth retardation (FGR) is
defined when the intrauterine weight of the foetus falls below the tenth percentile for the specified gest age
( ie. duration of pregnancy ) . Thus the precondition
of diagnosis of FGR demands accurate pregnancy dating. The other index of expressing IUGR is when the
estimated foetal weight falls below the two standard deviation below the mean.
A) How best to calculate the dating?? Ans:-LMP must be remembered correctly and
cycles must be regular, . If these are normal then hopefully dating if
gestation can be done correctly .Dating must be done with great accuracy so that the present
estimated foetal weigh can be
compared with the reference chart and diagnosis or
exclusion of FGR can be made. Now for every country there has been a
population based foetal weight standards are available
(Nomograms –Population Based studies)
i e foetal weigh as per USG for each
gestational age has been calculated and available to sonographer and
quite often such chart is incorporated
in the machine . Thus before the diagnosis
of FGR is made LMP must be known with
certainty. Otherwise false diagnosis of FGR will be made.
B) If LMP is unknown and neither dating USG or even NT scan are unavailable :-- In such a situation If LMP is not certain or unreliable then at least one obstetric USG carried out
at 16-18 week of gestation can be
used as a reference value about the duration of preg ( i e preg dating ) .However the cut off
value of diagnosis FGR is 10th
percentile weight for foetal age
against the standard week wt curve.
.Based on the Nomogam the foetus may
be :--
A)
Ag
A - appropriate
for gest age ( Babies born with birth weight between the 10 th and 90th percentile for gest age
B)
Lg
A- Large
for gest age - Foetus with
birth weight about the 90th percentile
C)
S
gA – small
for gest age ( < 10th percentile )
How do we know normal /
standard fetal weight as per gestational
week?
To
calculate this (country wise) women
with known LMP - estimation of foetal
wt is done at different
gestational age is done. Then
these foetal weights are plotted
against the gest weeks. These women must not have any disease and birth wt after delay should be
normal . Thus these pregnancies are essentially normal in all respects . This is also called
population standard or
“ growth curve “ or “ Reference Range
“ . Thus if a foetus exhibits 5th
percentile for wt in a particular gest age ( say 34 weeks ) it means
only 5% of healthy women of that
locality with normal birth wt ( proved
later ) will have such foetal weight.
Which term is better ?
FGR - Foetal Growth Restriction
IUGR=Intra
uterine growth restriction
SFD- Small
for date
Growth restricted foetus
Sg A –
small for gestational age .
The term retarted foetus .
Many women and
their family members think that the very word retardation of
foetus -à what have occurred in utero is irreversible . So
women & family
members got afraid
of the term retardation .So the present
nomenclature of this entity is growth restricted foetus . This means growth is temporally restricted which is
correctable by proper treatment
and it is not a permanent / irreversible damage.
FGR can manifest as a improper increase in uterine
length( SFH= Symphysis Fundal Height) ,
less maternal abdominal girth, clinically less liquor as felt
abdominally . The USG may reveal less
Head, Chest &
, Abd circumference c , subcut tissues
and muscle mass ( singly or in various
combination ) . Ideally all to such
measurements should be done to
diagnose FGR. But in practice all the
diameters / circumferences are not
measured .
How
accurate is USG in picking up FGR in pregnancies which are well dated??
Ans:- Even if all the parameters are used then also there can be missing of some FGR fetuses.
Limitations ore
fallacies of USG as a means of diagnosing FGR!!!
Ans:- Not only missing some cases of FGR by USG it is equally possible that ,even if all
the measurements are used then too there is a possibility that 15-75 % of
normal fetuses will exhibit
abnormal USG parameters and will be considered as FGR,
here lies the role of clinical expertise. .
How obstetricians used to diagnose FGR / SFD in the decal
of fifties / sixties when USG was not
widely available in India ?
The then clinicians used to assess foetal weight by the
followings but unfortunately
in many cases the presumption of
diagnosis of FGR was wrong
even by the most experienced
clinicians. Such measurements still do exist are done in each ANC care &
clinical examination mostly as a means of abd
palpation of foetus
1)
Measurement of vertical height
(Symphysis Pubis to Fundal Ht=SFH in cm
progressive increase).
è plotting
these figures symphysis to
fundal ht measurement
against calculated gestation age
2)
Obviously
there was no way of assessing foetal wt in utero by these ht & maternal abd
circumference measurement only a rough
gross assement of about weight of foetus could be made. Till date there is
no monogram which has been prepared with maternal wt gain, SFH in cm or abd
circumference in cm and expected foetal wt at that time, However
after the birth of the foetus exact wt can be measured as we always do
& follow. .
3)
There was no way of exactly knowing the foetal wt before birth. Hence appropriate
antenatal treatment for the FGR baby could not be instituted because
diagnosis of FGR could not be made antenatally . Now
with the advent of USG
if LMP is certain or if
gestation age has been calculated in
early preg then antenatal diagnosis of FGR
can be made with certainly and appropriate treatment for growth
affected baby can be instituted before
the birth of the foetus.
4)
How
to express foetal weight against reference
range ?
There are two methods
of expressing foetal wt
1) percentile method
1) percentile method
2) Standard deviation method
Classification of Symmetrical FGR (
30 % OF ALL FGR fetuses) ) : All the parts
of body
are symmetrically reduced I e
head trunk limbs . In such cases
the foetus is termed as symmetrical
IUGR
Asymmetrical FGR( 70% of all FGR fetuses)
When the foetal head
is disproportionately larger than the
other parts of body e.g. trunk limbs
. This is also called “Head sparing
IUGR “ --: because in this type if FGR
dimensions of head usually remains unaffected . Placental insufficiency is the main cause in this subtype
of IUGR. There is preferential blood flow to the foetal brain and that is the basis of Doppler study in IUGR .
Causes
of IUGR in asymmetric form
1)
Previous h/O
IUGR
2)
Hypertensive disorders of Preg
3)
Smoking
4)
Idiopathic
5)
Uterine anomaly
6)
Tumours
in Uterus
7)
A.P.H / Cardiac / Renal diseases of
mother
8)
multiple
gestation
Why we are worried about IUGR ? What is the significance
of diagnostic of FGR
The
complication of FGR foetus (
before birth ) and FGR or growth
affected body after birth are
as follows
1)
Ill effects of FGR on
the course of pregancy & labour : Premature
delivery
2)
Asphyxia
3)
IUFD
4)
Still
birth
So, to conclude let us agree that uncertainty remains
in the diagnosis of FGR even by USG done by
experts and therefore we to have to keep our
fingers crossed and hoping for arrival of yet another device to be introduced
which will exactly inform us about the foetal wt with great precision, more accurate
than current USG technology ,But that should be affordable are producible
and harmless to foetus and ease of op[keratin
by ward nurses.
No comments:
Post a Comment