Intended for healthcare professionals

Information In Practice

Identifying problems with data collection at a local level: survey of NHS maternity units in England

BMJ 1999; 319 doi: (Published 04 September 1999) Cite this as: BMJ 1999;319:619

Ultrasound dating data

Maternity data collection has probably been well ahead of most other
areas of health data collection but as Kenney and Macfarlane point out
there are considerable variations at local level which will not help in
the implementation of the National strategy of Information for Health.
One of the principles which I have learned while collecting maternity data
is that it is best to collect raw data rather than refined. I have been
particularly interested in the use of ultrasound dating but am frustrated
by the maternity database which contains only the EDD by ultrasound. This
gives no indication of the stage of pregnancy at which the scan data was
used, nor is there any opportunity to validate it. Ultrasound data is now
an integral part of the maternity record and this should really be
recorded directly from the ultrasound scanner into the maternity database.
I am not aware of any systems that allow this, although I do know of a
system which can read the data from the screen output. I feel pressure
ought to be put on the ultrasound machine manufacturers to provide an
electronic output of the data to an agreed protocol.

I have proposed a method for generating customised ultrasound dating
charts. (1) Unfortunately this requires raw ultrasound data and delivery
data which are rarely kept on the same database. I am proposing that
ultrasound dating charts should use the delivery of a live healthy baby as
the gold standard and the mean interval from a specific scan size to
delivery should be used to provide the "gestation". This has a number of
advantages. Firstly the "length" of pregnancy becomes irrelevant to the
calculation of the EDD, a subject of considerable controversy (2), and
secondly, large numbers of normal women, including those on the pill and
those who are unsure of their LMP can be included. These large numbers
allow the generation of customised charts and I have shown that small
differences are likely according to fetal sex, parity, maternal age (3).
Ethnicity is obviously another which I have not been able to test.


2. Hutchon DJR. Routine ultrasound is the method of choice for dating
pregnancy. Br J Obstet Gynaecol 1999:106;616

3. Hutchon DJR. Customised ultrasound dating charts. British Maternal
and Fetal Medicine Society. fourth Annual Conference, University of York.
Abstartcs - Journal of Obstetrics and Gynaecology 1999 19:suppl 1;s57

Competing interests: No competing interests

27 September 1999
David J R Hutchon
Consultant Obstetrician
Memorial Hosptial, Darlington