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Q: Why use a customised chart?
A: It improves the detection
of fetal growth problems and is now recommended
by the
RCOG Green top guidelines. See also summary
of evidence
Q: What do the lines on the chart represent?
A: The middle line is the
50th centile - showing the predicted median
curve for estimated fetal weight, and the upper
and lower lines are the 90th and 10th centiles,
respectively. Their slopes represent the range
of normal growth.
Q: Why plot estimated fetal weight
and not individual biometry - e.g AC, HC, FL
etc?
A: It is not possible to 'customise'
ultrasound parameters as there is no knowledge
of how they relate to measurments in the neonate.
In contrast, EFW relates to birthweight which
can be predicted and adjusted according to invidual
and pregnancy characteristics.
Q: How do we then differentiate between
symmetrical and asymmetrical IUGR?
A: There is no evidence that
a distinction between symmetrical and asymmetrical
growth is of benefit in accurately dated pregnancis
(ref: Gardosi J., Fetal and Maternal Medicine
Review 2002; 13 (4): 249-259). Furthermore,
for either type of IUGR, the recommended next
investigation is umbilical artery Doppler (see
RCOG Guidelines).
Q: How accurate is 'estimated fetal
weight'?
A: The random error is approx
10% in routine practice, although it can be
higher in very small and very large babies.
This is measured against the 'gold standard'
of birthweight. It contrast, there is no evidence
available on the accuracy of individual ultrasound
parameters.
Q: How often should we measure fundal
height?
A: Every 2-3 weeks; more often
would make the measurement error larger than
the expected increment over time; less often
would leave too long a time delay for reassurance
when growth is fine, or detection of abnormal
growth if present.
Q: Do we need to take account of descent
of the head when plotting fundal heigt?
A: There is no flattening
of the fundal height curve at term; even if
the head engages, the height of the uterine
fundus should continue to increase over time.
Q: How can fundal height be accurately
measured in obese women?
A: The measurements may plot
above the 90th centile but it is most important
to do measurements serially and to see whether
they follow the slope of the curve. If the woman's
size precludes confident fundal height assessment,
serial scanning should be considered.
Any more questions?
Please send them to:
grow@pi.nhs.uk
We will respond as quickly
as possible!
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