eMJA: Oats, Routine antenatal screening: a need to evaluate Australian practice

Editorial

Routine antenatal screening: a need to evaluate Australian practice

Are current screening practices evidence-based and cost effective?

MJA 2000; 172: 311-312

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Screening is defined as a procedure to identify, in an organised way, a specified disease or condition among asymptomatic individuals.¹ Before introducing a screening test into pregnancy care, it is imperative that the following criteria be met:

there is detailed knowledge of the effect of the condition on both the pregnant mother and her fetus;
a highly accurate and specific diagnostic test is readily available to make the definitive diagnosis;
the condition is a significant health problem;
the test and any actions based on its results are ethically acceptable to the community; and
increasingly important in the current climate of restricted healthcare funding, the economic implications of either performing or not performing the test have been evaluated.

As in many areas of medical practice, various screening tests have been introduced into obstetric practice without being evaluated according to these criteria, while others which might satisfy the criteria are not widely used.

Antenatal screening tests currently recommended by the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) are shown in the Box. In 1997, I surveyed use of a selection of these tests at the 11 hospitals then belonging to Women's Hospitals Australia (an Australian and New Zealand organisation which represents major women's hospitals; almost a quarter of Australian babies are cared for in member hospitals).

This survey revealed that, although all 11 hospitals routinely undertook a blood group and antibody screen, full blood count, tests for rubella antibody status and syphilis serology, and a second-trimester ultrasound examination, use of other tests was more variable. Tests for hepatitis B serology were routine at nine hospitals, urine microscopy and culture at four, measurement of serum -fetoprotein level at two, and the triple test for Down's syndrome at one.

The survey also revealed considerable variation in screening for gestational diabetes: six of the 11 hospitals screened all women, while the others selectively screened women with perceived risk factors (eg, maternal age over 30 years, family history of diabetes, poor obstetric history, maternal obesity, and ethnic group with high prevalence of diabetes). The RANZCOG does not recommend routine screening of all pregnant women for gestational diabetes, contrary to the guidelines of the Australasian Diabetes in Pregnancy Society.³ The place of screening for gestational diabetes and the criteria for its diagnosis are the subject of an international, multicentre project funded by the National Institutes of Health (US) -- HAPO (Hyperglycemia and Adverse Pregnancy Outcome). This should be completed in four years.

The low rate of screening for asymptomatic bacteriuria (also not recommended as a routine test by the RANZCOG²) is at variance with the recommendations of Rouse based on his analysis of published studies.⁴ He reported that, of the 2%-10% of pregnant women who have asymptomatic bacteriuria, 30% will develop acute and potentially serious infections. He concluded that screening and treatment prevents symptomatic infection and is cost effective.

Screening later in pregnancy for maternal carriage of group B streptococci (GBS) is also controversial. In this issue of the Journal, Connellan and Wallace describe the variation in GBS screening practices in Victoria.⁵ They recommend development of consensus practice guidelines to help prevent early-onset GBS disease in neonates (EOGBSD). Such guidelines have been developed in Queensland after a systematic review of the literature and a large Brisbane case-controlled study.⁶ The recommended strategy is not to perform routine antenatal screening but to consider administering intrapartum antibiotics for defined risk factors (preterm birth before 35 weeks' gestation; membranes ruptured for > 18 hours before delivery; maternal temperature 38ºC; GBS colonisation or GBS bacteriuria ever detected; or previous infant with EOGBSD) (Professor James King, Mater Perinatal Epidemiology Unit, Mater Misericordiae Mothers' Hospital, Brisbane, Qld, personal communication). The implementation of these evidence-based clinical guidelines is now being evaluated. This process could serve as a template for the evaluation and development of guidelines for all antenatal screening tests.

Routine screening for HIV is now recommended by the RANZCOG,² but most units do not comply with this directive -- in 1995, only 20% of pregnant women were so screened.⁷ The need to revise current policies, especially as antiretroviral drug therapy can reduce the risk of HIV transmission from mother to child from 30% to below 2%,⁸ was recently reviewed by Ziegler.⁹

In addition, calls for routine screening of thyroid function have followed publication of a study that found long-term developmental abnormalities in the offspring of women with even mild degrees of untreated hypothyroidism.¹⁰ The prevalence of undiagnosed hypothyroidism was 1.9 per 1000, and the offspring had a mean score on the Wechsler Intelligence Scale for Children four points lower than matched control children. To identify each at-risk fetus, 500 pregnant women would need to be tested. Again, this emphasises the pressing need for full analysis of the clinical and economic implications of such tests before they enter clinical practice.

Australia is not alone in the variation in screening practice. In a recent survey of obstetric centres in the United Kingdom, only 24% of births occurred in units with a universal testing policy for hepatitis B.¹¹ Conversely, universal screening for syphilis was the norm, although a number of centres were considering dropping this policy.¹¹

There is a paucity of accurate data on the cost of current antenatal screening practices to the Australian community. However, the economic impact is sure to be substantial. In 1997, 252 370 women gave birth in Australia.¹² If the RANZCOG screening recommendations were followed for all, then, based on the Medicare schedule fee structure, the annual cost would be around $48 million for routine haematological, serological, biochemical and cytological screening, and an additional $17 million for the triple test and hepatitis C serology.

Furthermore, in 1996-1997, Medicare benefits in excess of $33 million were paid for ultrasound examinations in pregnancy.¹³ Yates et al estimated in 1991 and 1992 that 97% of pregnant women had at least one ultrasound scan, and that 46% had two or more.¹⁴ It is not possible to calculate the cost of "routine screening" scans from these data. However, if all pregnant women have a second-trimester scan, the cost to Medicare is $25.5 million annually, with the cost to the community likely to be higher, as many scans are billed at rates above the Medicare schedule fee.

The introduction of first-trimester ultrasound scans of nuchal translucency, which identify up to 85% of fetuses with Down's syndrome¹⁵ and, potentially, fetuses with an increased risk of other structural abnormalities, including cardiac defects, will inevitably increase the number of routine ultrasound examinations. However, as these scans also identify fetuses with a low probability of Down's syndrome, they have the potential to reduce the numbers of chorionic villus samplings and amniocenteses performed in women with a high theoretical risk of trisomy 21. In addition, improvements in ultrasound resolution and our understanding of the markers of fetal anomalies may allow this late first-trimester scan to replace the second-trimester scan.

Although antenatal screening appears well accepted as a significant healthcare issue in Australia, it has not been subject to systematic assessment. The need for funding to critically evaluate all currently used tests seems self-evident. However, currently such funding has not been granted by the Commonwealth or State governments or Medicare, who carry the major financial burden for antenatal testing. The potential to redirect some of the healthcare dollar to other, needier areas is a further reason for appropriate funding to establish practitioner-credible, evidence-based practice.

Jeremy J N Oats
Director of Obstetrics and Gynaecology, Mater Misericordiae Mothers'
Hospital, Clinical Professor of Obstetrics and Gynaecology
University of Queensland, Brisbane, QLD
joatsATmater.org.au

Reprints: Professor J N Oats, Department of Obstetrics and Gynaecology, Mater Misericordiae Mothers' Hospital, Raymond Terrace, South Brisbane, QLD 4101.

Peters TJ, Wildschut HIJ, Weiner CP. Epidemiologic considerations in screening. In: Wildschut HIJ, Weiner CP, Peters TJ, editors. When to screen in obstetrics and gynecology. London: WB Saunders, 1996: 1.
Royal Australian and New Zealand College of Obstetricians and Gynaecologists Statements. 2.2. Screening in pregnancy. <http://www.ranzcog.edu.au/open/ statements/2_2.htm>
Hoffman L, Nolan C, Wilson JD, et al. Gestational diabetes mellitus -- management guidelines. The Australian Diabetes in Pregnancy Society. Med J Aust 1998; 169: 93-97.
Rouse DJ. Asymptomatic bacteriuria in pregnancy. In: Wildschut HIJ, Weiner CP, Peters TJ, editors. When to screen in obstetrics and gynecology. London: WB Saunders, 1996: 163-169.
Connellan M, Wallace EM. Prevention of perinatal group B streptococcal disease: screening practice in public hospitals in Victoria. Med J Aust 2000; 172: 317-320.
Flenady V, King J, Woodgate P, et al. Early onset neonatal GBS sepsis: a case controlled study. Proceedings of the 2nd Annual Congress of the Perinatal Society of Australia and New Zealand. Alice Springs, NT. 29 Mar-1 Apr 1998. Sydney: PSANZ, 1998.
Elford J, MacDonald MA, Gabb RG, et al. Antenatal HIV antibody screening in Australia. Med J Aust 1995; 163: 183-185.
Riley LE, Greene MF. Elective cesarean delivery to reduce the transmission of HIV. N Engl J Med 1999; 340: 1032-1033.
Ziegler JB. Antenatal screening for HIV in Australia: time to revise policies? Med J Aust 1999; 171: 201-203.
Haddow JE, Palomaki GE, Allan WC, et al. Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N Engl J Med 1999; 341: 549-555.
Newell M-L, Thorne C, Pembrey L, et al. Antenatal screening for hepatitis B infection and syphilis in the UK. Br J Obstet Gynaecol 1999; 106: 66-71.
Day P, Sullivan EA, Ford J, et al. Australia's mothers and babies 1997. Perinatal Statistics Series No 9. Sydney: Australian Institute of Health and Welfare National Perinatal Statistics Unit 1999; 7. (AIHW Cat No PER 12.)
Simes J. Diagnostic ultrasound: discussion paper. Presented at the Forum on Ultrasound. Sydney; 13-14 June 1998. Canberra: Australian Health Technology Advisory Committee, 1998: 41.
Yates JM, Lumley J, Bell RJ. The prevalence and timing of obstetric ultrasound in Victoria 1991-1992: a population-based study. Aust N Z J Obstet Gynaecol 1995; 35: 375-379.
Hyett JA, Perdu M, Sharland GK, et al. Increased nuchal translucency at 10-14 weeks of gestation as a marker for major cardiac defects. Ultrasound Obstet Gynecol 1997; 10: 242-246.

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