South African Society for Ultrasound
in Obstetrics and Gynaecology


Consent for early "routine" obstetric ultrasound

Howarth GR, Mulder P, Jeffery B.

Sometimes it is important to read narratives by patients to gain insight to how they perceive our "care".

"From a parent's point of view, when we are given appointments for scanning, particularly the first scan, it is offered in a very positive way. In fact we're not asked would we like to have a scan, it is done as a matter of course. The mother is told how she will be able to see her baby and it’s little hands and perfectly formed feet there before her eyes and that it actually does exist. Unfortunately, unknown to the expectant mother, the reason for the scanning is a negative one. When they are taking their measurements, little do we know they are looking for defects. They are not looking for healthy babies at all. In fact, the very opposite. They are looking for babies which may be handicapped in some way and then the procedure starts by offering tests and finally abortion"

This narrative is extremely insightful and gives us cause to reflect on the concept of routine obstetric ultrasound, in this case early ultrasound scanning. Explicit in the narrative and probably pervasive in much of contemporary obstetric practice is the absence of any informed consent prior to obstetric ultrasound. Indeed the perception is often created that ultrasound forms part of normal routine antenatal care. Additionally the presumption is often that the mother wants to know if her baby is potentially abnormal, to concern herself with or indeed to continue with the cascade of intervention that may follow an abnormal screening test. When performing these ultrasounds we often forget the detrimental side effects of screening, the anxieties, the false alarms, the unnecessary interventions and over-management and from a potential medico-legal point of view, false reassurances.

For the purposes of this paper early ultrasound refers to an ultrasound performed either late in the first or early in the second trimester of pregnancy, on an asymptomatic low risk obstetric patient. The decision to have an ultrasound or not revolves around informed choice. To make this decision the patient requires information and should she then decide to have an ultrasound she can then give her authorisation.

The basic structure of the informed consent process is summarised in table 1.

Regarding informed consent and obstetric ultrasound, once one has accepted that informed consent is an obligation.' the major issues surround disclosure of information (see table 2). One does however have to be aware of other factors. Amongst them the very "routine-ness" of the procedure may interfere with the woman's voluntariness, in the sense that she may feel compelled to have the examination as it is considered to be routine. In many cases there is a potential conflict of interest that the patient should be informed about. The person offering and performing the scan will usually benefit financially as a result of the scan being performed and quite possibly as regards any further management of the case. Following disclosure of information women should also be given time to reflect prior to and after having made a decision.

The physical risks of obstetric ultrasound itself are more theoretical than real. There is no consistent evidence of fetal damage occurring as a result of exposure following screening ultrasound in pregnancy (Dooley 4-8) and at present, there is no clear evidence that the ultrasound examination itself is harmful (Neilson).

An early obstetric ultrasound is both a diagnostic and a screening procedure. It is diagnostic in confirming fetal life, placental localisation, evaluating chorionicity and the number of fetuses in the case of multiple pregnancies and fetal measurements, to confirm or establish gestational age while it is a screening test for chromosomal and structural fetal abnormalities. Amongst other things table 2 shows the General Medical Council's guidelines for information to be disclosed pertaining to screening and diagnostic tests.

1. Screening component:
Not detecting an abnormality is often equated with negligence as most pregnant women have an anticipation of perfection of outcome and unrealistic expectations of screening or diagnostic tests. Doctors must try and establish a reasonable level of understanding and expectation in their patients.

Patients need to acquire a basic conceptual understanding of the concepts of prevalence, sensitivity, specificity, and positive and negative predictive values. Prevalence is the easiest to understand; chromosomal and major structural abnormalities are rare and there risks may be presented as either ratios or percentages. Sensitivity, specificity, positive and negative predictive values are more difficult concepts to comprehend. Patients may grasp them more intuitively if one utilises the concepts of true positives, false positives, true negatives and false negative. A patient should understand that a test may be positive; if positive it may be a true positive or a false positive. False positives are a reality of any screening program, they are alarming and anxiety provoking and usually lead to further testing, which if invasive are a potential risk to the normal fetus. If the test is negative it may be a true negative or a false negative. Like false positives, false negatives are a reality of any screening program, they are falsely reassuring and if not explained and understood may lead to subsequent litigation. The patient should also understand that as a result of the low prevalence of both chromosomal and structural abnormalities the majority of positive screening results will be falsely positive, while fortunately the overwhelming majority of negative screening results are true negatives.

As in other areas of medicine one has the problem of extrapolating population based risks to an individual patient. As an example the population-based risk of loosing a pregnancy due to an amniocentesis may well be 0,5% (1.200) and 1% (1:100), but in reality the risk for the patient it is all or nothing. She either retains or looses the pregnancy, the risks to the individual are either zero or one hundred percent.

1.1 Screening for chromosomal abnormalities.

For the purposes of this paper we will limit ourselves to nuchal translucency evaluation in isolation for detecting chromosomal abnormalities. So as to simplify the discussion we will also restrict ourselves to the detection of trisomy 21.

As regards the risk of a woman carrying a trisomy 21 fetus, all women have a risk of carrying a chromosomally abnormal fetus. The risk of trisomy 21 increases with maternal age and decreases as gestational age advances as spontaneous fetal death is more likely for trisomy 21 that for normal pregnancies.

A recent multicentre study scanned 100311 singleton pregnancies and had analysable data on 96 127 cases. Of the 326 trisomy 21 fetuses they correctly diagnosed 268, giving them a sensitivity of 82,2%. Using a risk cut-off of 1/300, 7907 patients were considered to have a positive screening test. From this we can see that of the 7907 abnormal screening tests only 268 were true positives and 7639 were false positives. All 7907 patients with an abnormal screening test had to deal with the anxiety of it and required invasive testing to exclude trisomy 21. About 30 invasive tests are required to identify one affected fetus. If the accepted pregnancy loss for invasive testing is between 1:200 and 1:100, theoretically between 38 and 76 normal babies could be lost as a result of invasive testing (RCOG quotes loss rate of 1.100). The screening test was negative in 88 220 cases, of which 58 were false negatives. Fifty-eight patients had a fetus with trisomy 21 despite a negative screening test and they were falsely reassured of normality.

As in identification of structural abnormalities, accuracy of diagnosis of chromosomal abnormalities utilising nuchal translucency appears to be dependent on operator training and skill. Nuchal translucency screening using less well-trained operators has reported significantly worse results.

Patients should also be told that combining serum markers and nuchal translucency screening improves both the sensitivity and the specificity and hence also improve the positive and negative predictive value for detecting trisomy 21.

1.2. Screening for structural abnormalities.

The prevalence of major structural abnormalities is low and in the region of 1 % to 2% of all births. It should be explained that at least a third of major structural abnormalities cannot be detected by ultrasound and that the reported sensitivities for ascertaining those that can be detected vary considerably (Dooley).

It must be stressed that the majority of work on detecting structural abnormalities on routine ultrasound has been done on ultrasounds performed much later in the second trimester. The sensitivity of obstetric ultrasound examination for the detection of fetal abnormalities logically varies by experience and training, by the nature and the severity of the malformation, by the gestational age of the fetus and by the presence or absence of an indication for the ultrasound (Seeds).

The recent Multicentric Eurofetus Study showed routine screening ultrasound to have an overall sensitivity of 74% for major structural defects.

In the hands of experts late first / early second trimester ultrasound has been shown to have a similar sensitivity for identifying major structural abnormalities. Larger studies will however have to be performed to confirm the accuracy of early ultrasound in identifying structural abnormalities.

The patient should understand that even identifying a structural abnormality makes little difference to overall outcome in the majority of cases. Where a lethal abnormality is detected the scan may make a difference as to whether the death occurs in-utero as opposed to neonatally. The vast majority of non-lethal abnormalities are not amenable to intervention. As practitioners we should never under-estimate the concern and anxiety caused when we are concerned about the presence of a possible abnormality and refer the patient to a more experienced ultrasonologist. This anxiety persists, possibly to a lesser extent, even if the experienced ultrasonologist does not share your concern.

2. Diagnostic component:

Early ultrasound is diagnostic in confirming fetal life, placental localisation, evaluating chorionicity and the number of fetuses in the case of multiple pregnancies and fetal measurements to confirm or establish gestational age. Scanning asymptomatic patients at 12-13 weeks will reveal that approximately 2% will have missed abortions. Elective treatment of these cases reduces the number of emergency admissions with concomitant improvements in the safety of car. rf these patients.

Other advantages from diagnostic information from these scans may be a putative rather than actual. Only 10% of low placentas at second trimester scan remain low at term and in most pregnancies with placenta praevia a clinical indication will arise for diagnostic ultrasound, thus the role for screening fro placenta praevia is debatable (Bricker & Neilson). Early detection of twin pregnancies has not been translated into an improvement in outcome (Neilson). The majority of mothers who present for an early ultrasound have a known and accurate last menstrual period, and are not victims of superimposed medical conditions that may adversely impact on fetal development, and most pregnancies demonstrate normal clinical progress toward a term delivery of a normal living child. Gestational age is known and the only shown benefit is fewer inductions are performed for possible post-datism.

It has been suggested that the future of obstetric and gynaecological litigation lies in the fields of obstetric ultrasound and cervical cytology. Practitioners that possibly would like to take refuge behind the fact that many of their colleagues do not take informed consent prior to routine ultrasound should beware. A patient is entitled to informed consent and failure to take adequate consent may result in admonishment. Paradoxically even if one does offer early obstetric ultrasound, patients that present early enough in pregnancy should be counselled on the possibility as they and not the doctor should be the arbitrator in deciding on whether to have the ultrasound or not. The possibility of the intervention with its potential advantages creates a moral and legal imperative of disclosure. The guidelines in this paper are specific for informed consent for early obstetric ultrasound and informed consent for ultrasound later in pregnancy is essential and is dependent on the indications for the ultrasound and the potential risks and benefits involved.

The courts are under no obligation to compare the practitioners practice to contemporary practice or the opinion of experts. The precedent has been set in South African law and the standard of disclosure is dependent on the information that a reasonable patient would require prior to intervention. The standards of disclosure expected by the health professionals' regulatory bodies might be higher than the minimum required by law. The General Medical Council in the United Kingdom advises the doctor should try and ascertain the patients' individual needs and priorities when providing information about management options. For them the standard of disclosure is dependent on the subjective standard of the individual on whom the procedure is to be performed.

Surely any true moral agent would also feel obliged to inform a patient fully prior to any intervention? Fully informing the patient prior to the ultrasound also facilitates post ultrasound counselling should the examination have revealed an abnormality. Obtaining informed consent also serves the interests of the physician by reducing the risk that subjects will pursue legal actions when their expectations about the intervention are not met. The possibility of later unhappiness and even litigation may be greatly reduced by early disclosure, discussion, and the opportunity to decline intervention. The importance of informed consent cannot be over-emphasised. Informed consent should be seen as a friend not a fiend, help not a hindrance.

Table 1: The basic structure of the informed consent process
(From Beauchamp and Childress)

Informed consent is not only a moral but also a legal obligation.
Common law has established the general principle of informed consent. Touching a patient without valid consent could constitute assault (C).
Further if a health professional fails to obtain adequate consent and the patient subsequently suffers harm as a result of the treatment, albeit it as a result of adequate treatment and inherent risl- '."is may be a factor in a claim of negligence against the health professional involved (C).

1. Threshold elements
1.1 Voluntariness: Any decisions made should be free of undue pressure. The anticipation by the doctor that a scan is to be done may interfere with a patient's voluntariness.

1.2 Decision making capacity: The patient should have the mental capacity to understand and make a decision about the procedure for which consent is being taken, as well as the ability to communicate their decision. In adults in the absence of compelling evidence to the contrary there should be a presumption of decision-making capacity.

2. Informational elements
2.1 Disclosure of information: Legally the doctor has to exercise due care by giving the necessary information. Morally the doctor has to give the information necessary for the patient to make an autonomous decision. The patient should also be informed that the purpose of the consent process is to facilitate her autonomous choice.

2.2 Recommendations: The doctor should give the beneficence -/ nonmaleficence- based recommendations.

2.3 Understanding: Prior to accepting a patient's authorisation the doctor should ascertain whether the patient has a substantial understanding of the salient facts.

3. Consent elements

3.1 Decision: The patient makes a decision based on the information disclosed. The decision is made according on the patient's own value system. The patient may decide to consent or decline the ultrasound.

3.2 Authorisation: If the patient decides to consent to the intervention authorisation is given. There is no obligation for written authorisation and in the case of routine antenatal ultrasound oral authorisation is probably satisfactory. Should the patient decline the routine ultrasound examination it would probably be prudent to note this in contemporaneous notes.

It should be emphasised that the individual providing the treatment or investigation is responsible for ensuring that the patient has given valid consent before treatment begins ©.


When a doctor’s diagnostic or therapeutic skills are evaluated in court, should they comply with what a body of reasonable medical practice considers good practice then they must be accepted. This is not the case as regards the disclosure of information for informed consent. Although the evidence of expert medical practitioners as to the completeness of disclosure may be persuasive, it will not be conclusive if the court finds that the standard of disclosure does not comply with the doctors legal duty.

What the law is saying is that the level of disclosure is not dependent on the professional practice standard of disclosure as determined by the profession, but what the court considers a reasonable person would want to know prior to intervention. The standard of disclosure expected by health professionals' regulatory bodies might be higher than the minimum required by law. The General Medical Council in the United Kingdom advises the doctor should try and ascertain the patients' individual needs and priorities when providing information about management options.

For them the standard of disclosure is dependent on the subjective standard of the individual on whom the procedure is to be performed.

Legal disclosure should include:
1. Advantages and disadvantages of the intervention, "significant" risks of the intervention.
2. Alternatives to the intervention.
3. Risks incurred by declining the intervention.
4. The option of a second opinion.

The term informed consent was initially legal in origin. From a moral viewpoint, taking informed consent has less to do with legal liability of disclosure and more to do with respecting the autonomous choice of the patient (B&C). Ethically the doctor also should try and ascertain the patients' individual needs and priorities when providing information about management options. Disclosure should include informing the patient that the reason for taking informed consent is to facilitate the patient's autonomy. Also explain that consent has limitations and the patient may change their mind. The quality of informed consent as a process is more important than the quantity of information disclosed.

The General Medical Council in the United Kingdom has given guidelines with respect to obtaining informed consent from patients undergoing medical procedures, including screening or diagnostic tests. The guidelines are specific and state information that the following should be explained

1 . The purpose of the test and whether it is a screening or diagnostic test and the distinction between the two.
2. The likelihood of a positive and negative test.
3. The concepts of sensitivity, specificity, false- negative and false positive findings.
4. The uncertainties and risks of the screening.
5. The significant medical, social or financial consequences of screening.
6. Follow up plans, including counselling and support services.