Ultrasound biosafety: Knowledge and opinions of health practitioners who perform obstetric scans in South Africa

BACKGROUND

Diagnostic ultrasound is generally considered as a safe test in pregnancy. To date there is no evidence that ultrasound has caused harm to the developing foetus. However, with the number of obstetric scans on the rise and the steep increase in acoustic output achieved by modern machines, the lack of evidence of absolute safety remains a concern. Acoustic output is under the direct control of the operator and is therefore the operator's responsibility to keep the intensity as low as reasonably achievable. A situation analysis in the South African context was deemed necessary to determine end user knowledge and opinions on safe antenatal ultrasound practice.

AIM

The aim of this quantitative descriptive, cross-sectional study was to evaluate the knowledge and practice of health practitioners who perform antenatal scans regarding safety aspects of diagnostic ultrasound.

SETTING

A self-administered questionnaire was distributed at two national congresses, hosted by the South African Society of Ultrasound and Obstetrics (SASUOG) and South African Society of Obstetricians (SASOG) committees.

METHOD

Quota non-probability sampling allowed for the identification of professional categories capable of providing information relevant to the study objectives. The sample represented a population with experience in obstetric ultrasound.

RESULTS

Compared to international studies, South African end users demonstrated better knowledge of safety indices than their international counterparts. It is, however, discouraging that end users still demonstrate insufficient knowledge regarding factors contributing to adverse biological effects.

CONCLUSION

With room for improvement, an effort should be made to comply with international standards through increased training efforts and raising awareness.

Imaging Pregnant and Lactating Patients

As use of imaging in the evaluation of pregnant and lactating patients continues to increase, misperceptions of radiation and safety risks have proliferated, which has led to often unwarranted concerns among patients and clinicians. When radiologic examinations are appropriately used, the benefits derived from the information gained usually outweigh the risks. This review describes appropriateness and safety issues, estimated doses for imaging examinations that use iodizing radiation (ie, radiography, computed tomography, nuclear scintigraphy, and fluoroscopically guided interventional radiology), radiation risks to the mother and conceptus during various stages of pregnancy, and use of iodinated or gadolinium-based contrast agents and radiotracers in pregnant and lactating women. Maternal radiation risk must be weighed with the potential consequences of missing a life-threatening diagnosis such as pulmonary embolus. Fetal risks (ie, spontaneous abortion, teratogenesis, or carcinogenesis) vary with gestational age and imaging modality and should be considered in the context of the potential benefit of medically necessary diagnostic imaging. When feasible and medically indicated, modalities that do not use ionizing radiation (eg, magnetic resonance imaging) are preferred in pregnant and lactating patients. Radiologists should strive to minimize risks of radiation to the mother and fetus, counsel patients effectively, and promote a realistic understanding of risks related to imaging during pregnancy and lactation.

Early functional and morphological brain disturbances in late-onset intrauterine growth restriction

AIMS

To determine whether the brain disturbances develop in late-onset intrauterine growth restriction (IUGR) before blood flow redistribution towards the fetal brain (detected by Doppler measurements in the middle cerebral artery and umbilical artery). Further, to evaluate predictive values of Doppler arterial indices and umbilical cord blood gases and pH for early functional and/or morphological brain disturbances in late-onset IUGR.

STUDY DESIGN

This cohort study included 60 singleton term pregnancies with placental insufficiency caused late-onset IUGR (IUGR occurring after 34 gestational weeks). Umbilical artery resistance index (URI), middle cerebral artery resistance index (CRI), and cerebroumbilical (C/U) ratio (CRI/URI) were monitored once weekly. Umbilical blood cord samples (arterial and venous) were collected for the analysis of pO2, pCO2 and pH. Morphological neurological outcome was evaluated by cranial ultrasound (cUS), whereas functional neurological outcome by Amiel-Tison Neurological Assessment at Term (ATNAT).

RESULTS

50 fetuses had C/U ratio>1, and 10 had C/U ratio≤1; among these 10 fetuses, 9 had abnormal neonatal cUS findings and all 10 had non-optimal ATNAT. However, the total number of abnormal neurological findings was much higher. 32 neonates had abnormal cUS (53.37%), and 42 (70.00%) had non-optimal ATNAT. Furthermore, Doppler indices had higher predictive validity for early brain disturbances than umbilical cord blood gases and pH. C/U ratio had the highest predictive validity with threshold for adverse neurological outcome at value 1.13 (ROC analysis), i.e., 1.18 (party machine learning algorithm).

CONCLUSION

Adverse neurological outcome at average values of C/U ratios>1 confirmed that early functional and/or structural brain disturbances in late-onset IUGR develop even before activation of fetal cardiovascular compensatory mechanisms, i.e., before Doppler signs of blood flow redistribution between the fetal brain and the placenta.