Ultrasound scans Part 3: Key Questions to Consider

In our third and final part of our ultrasound series, we’ll look at key questions to consider when planning or attending for an ultrasound.

Ultrasounds in pregnancy have become so routine, that we rarely question their use. However here are some key questions you may want to consider:

1. How do ultrasound scans work?

Ultrasound scans, often referred to simply as scans, sends out high-frequency sound waves into your uterus. These sound waves bounce off your baby, producing echoes. These echoes, in turn become an image on a screen which allows a trained medical professional, called a sonographer, to read the images to measure your baby’s growth, check his or her movements and positions, and check for concerns to your baby, the placenta, or your cervix. Over the course of a scan, low levels of heat are generated and is absorbed on the part of your baby which is being scanned. For this reason, scans are recommended for diagnostic purposes only.

2. Are routine antenatal scans safe?

Ultrasound scans have never been proved to be unsafe; this is quite a different thing to ultrasound scans having been proved to be safe. For this reason, ultrasounds are recommended for diagnostic purposes only.

The American College of Obstetricians and Gynecologists (ACOG) has endorsed the following statement from the American Institute of Ultrasound in Medicine (AIUM) discouraging the use of obstetric ultrasonography for non-medical purposes (eg, solely to create keepsake photographs, videos): “The AIUM advocates the responsible use of diagnostic ultrasound. The AIUM strongly discourages the non-medical use of ultrasound for psychosocial or entertainment purposes. The use of either two-dimensional (2D) or three-dimensional (3D) ultrasound to only view the fetus, obtain a picture of the fetus or determine the fetal gender without a medical indication is inappropriate and contrary to responsible medical practice. Although there are no confirmed biological effects on patients caused by exposures from present diagnostic ultrasound instruments, the possibility exists that such biological effects may be identified in the future. Thus ultrasound should be used in a prudent manner to provide medical benefit to the patient.” American College of Obstetrics and Gynecology (ACOG)

No well-controlled study has yet proven that routine scanning of prenatal patients will improve the outcome of pregnancy.

In many areas within maternity care settings, the only acknowledged risks with ultrasound scanning appears to be of inexperienced operators getting false results and the series of cascading events associated with that. Other evidence raises questions of the perceived benefits of antenatal ultrasound and suggests a need for further research.


3. How much ultrasound is my baby getting?

The answer is you probably don’t know and nor does anyone in the unit you have attended. The answer will lie in some combination of the number of exposures, the intensity of the exposure, the location of the exposure and the length of time of the exposure. When a midwife listens to the foetal heartbeat with a soniciad or similar hand held device this has an advantage in that you can also hear the baby’s heartbeat and it is comforting and reassuring. However this technology comes with a price.

Many women do not realise that their baby is being exposed to Dopplar ultrasound, albeit a small dose. Dating scans, developmental scans and routine antenatal visits scans enable more exposure. Doppler ultrasounds to assess maternal–foetal blood flow can sometimes mean the baby is exposed to both continuous and pulsed wave Doppler ultrasound. Electronic Foetal Monitoring (EFM) also uses ultrasound, and we know there is no benefit associated with EFM even for high-risk mothers. Then there is the issue of length of exposure and of the intensity of the exposure. Some exposures are shorter than others (eg Sonicaid vs developmental scan) and some travel through less maternal tissue than others (eg trans-vaginal vs trans-abdominal scans). Exposure could be minimised by:

1. Only having an ultrasound when medically indicated

2. Minimising exposure time

3. Minimising the exposure intensity

AIMS UK suggest that ultrasound exposure should form part of your antenatal record and have a form that you can ask your care giver to fill in should you want to document the amount of ultrasound your baby is exposed to in-utero.

4. Are there significant perinatal and maternal benefits to having routine ultrasound examinations?

The jury appears to be out on this given the false positives and false negatives associated with second trimester diagnostic and dating scans. Perinatal mortality rates in countries where abortion is available seem to show improvement with routine ultrasound scans but this is because babies with a gross abnormality are aborted and therefore do not die soon after birth which in turn lowers the perinatal mortality rate.


5. Who carries out scans?

Does every person scanning your baby have the same level of expertise? The answer is no. Trained radiographers will have more experience and training than obstetricians and midwives. The national guidelines for early foetal assessment has ensured that in early scans a base level of expertise is required, but this guideline does not extend to later scans.

6. Does a scan allow you to bond with your baby or is it a gross invasion of its in-utero privacy?

Mothers are very much divided on this issue as many mothers enjoy the reassurance of seeing their baby moving. Others argue this causes mothers to become reliant on technology to be sure of their baby’s well being.

7. Were you asked for your full informed consent for an ultrasound scan?

AIMS Ireland believes that women should be informed of the purpose of each type of ultrasound scan so that they can decide whether it has benefits for them. A crucial part of this informed consent should be the accuracy of results at the unit in which the investigation is being carried out.

With this knowledge you might wish to opt out of a dating scan in early pregnancy if you are sure of your dates, or you may wish to have an early dating scan but not an abnormality scan. Ultimately the decision is yours.

Birth Photography

Additional points to consider

Ultrasound – Perceived Benefits?

A large study – Effect of Prenatal Ultrasound Screening on Perinatal Outcome – showed that routinely giving women 2 ultrasound scans in pregnancy did not reduce morbidity or mortality of babies of low risk women.

“There were no significant differences in the rate of preterm delivery, distribution of birth weight, or outcomes within the subgroups of women with multiple gestations, small-for-gestational-age infants, and post-date pregnancies. Finally, the detection of major anomalies by ultrasound examination did not alter outcomes.”

The same study also showed that when looking at women in high risk subgroups, also found there was:

“no significant difference in the frequency of adverse perinatal outcome. A change in the length of gestation and the distribution of birth weight would be expected if an intervention improved perinatal outcome in multiple-gestation pregnancies or among small-for-gestational-age infants, but none was found”

In another study, half of the estimated weights of babies by scan were incorrect. And another study of diabetic women found:

“Even regular serial scanning and clinical examination will not always diagnose the macrosomic fetus in diabetic pregnancy. In our hands, clinical examination is as predictive as ultrasound measurements. Ultrasound does add to clinical prediction power but only to a small extent. Ultrasound should be used in a selected way, as defined by clinical findings, and with recognition and understanding of the errors and biases involved”

Raising Questions – Further Research

Other research has highlighted issues which show the need for further research into ultrasound. In 1999, a Swedish paper in the Journal of Epidemology suggests that ultrasound may cause the possibility of slight changes in brain development in boys. The study compared men born to mothers who had scans vs men born to mothers who had not had scans during their pregnancies. The results concluded that the scan group had a 30% increased rate of left-handedness compared to the non-scan group. Researcher Prof Juni Palmgren of the Karolinska Institute in Stockholm on the team’s findings:

“I would urge people not to refuse ultra-sound scanning as the risk of brain damage is only a possibility – but this is an interesting finding and needs to be taken seriously.”

Related Reading – Evidence and Guidelines

ACOG: Nonmedical use of Obstetric Ultrasonography


Ultrasound Surveillance in the High risk patient -Does it Deliver?

Scans may ’cause brain changes’: http://news.bbc.co.uk/2/hi/health/1699905.stm

Safety Assurance in Obstetrical Ultrasound: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2390856/

Effect of Prenatal Ultrasound Screening on Perinatal Outcome: http://www.nejm.org/doi/full/10.1056/NEJM199309163291201#t=articleBackground

Clinical and ultrasound prediction of macrosomia in diabetic pregnancy

Other articles in this series:

Ultrasound Scans Part 1: How can a scan help you and your baby?

Ultrasound Scans Part 2: Types of scans

Comments are closed.