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Informed consent to undergo serum screening for Down's syndrome: the gap between policy and practice

Psychology and Genetics Research Group, United Medical and Dental Schools of Guy's and St Thomas's Hospitals, Guy's Campus, London SE1 9RT University of Wales College of Medicine, Cardiff CF4 4XN Correspondence to: Dr Marteau.

The funding of antenatal screening programmes for Down's syndrome often emphasises laboratory aspects of the tests to the neglect of the counselling components. It is widely agreed that the decision about whether to undergo prenatal screening should be made by the pregnant woman on the basis of good information.¹ The high uptake of screening in some hospitals has brought into question the adequacy of information given about the tests before women undergo them.² To make informed decisions about whether to undergo testing women need to know what conditions the test might detect as well as the implications of negative and positive results. Such information may also be of benefit in preparing women for possible adverse outcomes of screening.³

We assessed knowledge about different aspects of serum screening for Down's syndrome in women being offered such tests. This provides an index of how well the counselling aspect of the programmes is being conducted.

Subjects, methods and results

The study subjects comprised 353 pregnant women of up to 18 weeks' gestation who attended one of five hospitals in the United Kingdom that currently offers routine serum screening for Down's syndrome. They provided baseline data as part of an intervention study to improve the communication skills, and ability to give information of midwives and obstetricians.⁴ women completed questionnaires after a consultation with either a midwife or an obstetrician; during the consultation routine antenatal screening tests, including serum screening for Down's syndrome, were offered. Their knowledge was assessed by using a multiple choice questionnaire with nine items. The internal reliability of the questionnaire was measured by using Cronbach's (alpha), which gave a coefficient of 0.66.

The amount of variance in knowledge predicted by demographic variables was assessed by performing discriminant function analyses for each item of the questionnaire. The demographic variables were age, number of children socioeconomic class, and ethnicity. The table shows the proportions of women giving correct responses to the nine items and the variance predicted by the demographic variables.

Proportions of women knowing about aspects of screening for Down's syndrome
-------------------------------------------------------------------------------
                                                  No (%) of      Variance
                                                 women with    predicted by
                                                   correct        patient
                                                  knowledge     demographic
Information about test                             (n=353)     variables (%)
-------------------------------------------------------------------------------
Test is offered to all women                      262 (74)          11
Test is performed at 16-18 weeks of
  pregnancy                                       314 (89)          14
Maternal blood sample is used for test            254 (72)          18
Test screens for Down's syndrome                  134 (38)           5
Results take 1-2 weeks to come back               142 (40)           5
About 5% (1 in 20) women are recalled              45 (13)           4
Further tests are offered if result is positive   238 (67)          15
Most women with positive results have
  normal babies                                   112 (32)           3
Negative results do not guarantee that
everything is alright with baby                   127 (36)          12

Comment

Though women in this sample were knowledgeable about practical aspects of undergoing the test, they were less well informed about aspects of the test that could inform their decisions about whether to undergo testing and prepare them for possible adverse outcomes such as being recalled with a high risk result or giving birth to an affected child after a result indicating low risk.

The demographic variables were weak predictors of the variance in knowledge, particularly items on which fewer than half the women gave the correct answer. The pattern of women's knowledge reflects the observed emphasis of midwives and obstetricians when routinely informing women about prenatal screening.⁵ information about the practical aspects of the test is emphasised, whereas information about the likehood and implications of possible results is rarely given.

These results highlight the extent to which prenatal screening programmes are falling short of the counselling standards that have been set.¹ In addition to the setting of guidelines, effective staff training is needed to teach health professionals how to present prenatal screening tests in ways that will lead to informed decision making by patients.⁴

This study was funded by the Medical Research Council. TMM and DKS are supported by the Wellcome Trust.

1. Royal College of Obstertricians and Gynaecologists. Report of the RCOG working party on biochemical markers and the detection of Down's syndrome. London: RCOG Press 1993.
2. Round A, Hamilton W. Prenatal screening for Down's syndrome. BMJ 1993;307:1211. [Free Full Text]
3. Weinman J, Johnston M. Stressful medical procedures: an analysis of the effect of psychological interventions and the stressfulness of the procedures. In: Maes S, Spielberger CD, Defares PB, Sarason IG, eds. Topic in health psychology. London Wiley, 1988:205-17.
4. Smith DK, Shaw RW, Slack J, Marteau. TM Training obstetricians and midwives to present screening tests: evaluation of two brief interventions. Prenat Diagn (in press).
5. Marteau TM, Slack J, Kidd J, Shaw RW. Presenting a routine screening test in antenatal care: practice observed. Public Health 1992;106:131-41. [Medline]

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