Chapter 15         Development of Pro-Forma


15.1         Routine Scan Pro-forma

Each obstetric ultrasound examination performed is usually accompanied by a sonographer’s report which conveys the measurements and findings to the reporting physician.  Depending upon the format of the report it may also serve as a reminder and guide for the sonographer that assists in the methodical performance of the scan and ensures that all measurements are taken and all anatomical areas of the fetus examined. 

 

The ASUM and RACOG have a produced a recommended protocol for the performance of the obstetric ultrasound examination in Australia, as have the AIUM in conjunction with the ACR for the United States of America.  Based on these recommendations a pro-forma was designed for all second and third-trimester pregnancy ultrasound examinations in the Geelong Hospital Ultrasound Department to guide the sonographers through a minimum standard examination.  This, with the ASUM protocol, is reproduced in the Appendix.

 

The range of anatomical areas covered by this pro-forma and the techniques used by the sonographers to examine those areas provide a very comprehensive survey of the fetus.  Many of the ultrasound markers for chromosomal abnormality are covered by this standard survey.  If, during the course of a standard examination an abnormality is detected in the fetus, placenta, cord, amniotic fluid volume or in regards to fetal growth, an even more comprehensive fetal survey is undertaken.  An extra form is used in these situations: the chromosomal marker pro-forma.

 

15.2         Chromosomal Marker Pro-forma

The search for fetal anatomical abnormalities can only be as good as the sonographer’s knowledge of the range of abnormalities and their ultrasound appearances.   Many articles stress the need for a search for other abnormalities when one is found, but only rarely do they list what the search should entail.  This may give the sonographer the impression that the views included in a standard scan are enough to exclude those other abnormalities. 

 

In order to augment the search for chromosomal markers, a second pro-forma was developed for The Geelong Hospital which listed as many potential ultrasound markers for aneuploidy as could be found.  This was developed from the literature review which was used for this thesis. 

 

 The current (Westmead) pro-forma is reproduced in the Appendix.  Although many of these markers are potentially visible on the standard examination, in the extended examination emphasis is placed on the quality of the examination, which must be unimpeachable.  In particular, views of the heart must be of the highest possible quality.  If fetal position obviates an excellent examination, the patient may be rescanned after a period of time has elapsed for the fetus to move; usually 20-30 minutes is sufficient.  If maternal obesity or scar tissue obviate an excellent examination, the patient may need to be rescanned at later stage of pregnancy, although this is not always possible or even successful in extreme obesity. 

 

The extended list on this pro-forma may seem daunting at first.  However, most of these abnormalities can be assessed as part of the routine scan in normal fetuses within the time allowed on most institutions.  Very view extra images would actually be required.  For example, the  fronto-thalamic measurement is made on the BPD image, as are the exclusion of agenesis of the corpus callosum, abnormal cephalic index and strawberry shaped head.  Extra views may be required for ear and iliac wing measurement, and for confirmatory views of the hands, feet and toes in coronal, transverse and sagittal planes.  Most cardiac defects should be identified on four-chamber and out-flow tract views, although judicious use of colour Doppler may assist64.

 

15.3         Conclusion

The use of a sonographer’s pro-forma may assist in the thorough assessment of the fetal morphology.  An extended checklist is used whenever an abnormality is detected.  Such a protocol would assist in the detection of extra malformations to affect the risk of chromosomal abnormalities and therefore be a guide for genetic counselling.