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Congenital anomalies and landfill sites - analyses require high quality data.
- Judith Greenacre (11 February 2000)
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Judith Greenacre, Consultant in Public Health Medicine Swansea NHS Trust, Singleton Hospital, CARIS Office
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EDITOR,
As founders of the Welsh Congenital Anomaly Register & Information Service (CARIS) , we are all too aware of the difficulties with congenital anomaly data mentioned by Fielder et al. 1 and Dolk.2 Analysis of our first year's data (1998) has confirmed the suspicion of previous substantial under-reporting to the National Congenital Anomaly Monitoring System.3 As CARIS data are only available from 1998 and numbers are small, we are unable to reproduce Fielder's study concerning mid line abdominal wall defects. We can however report the numbers of cases of all anomalies reported in 1998 for the wards surrounding the Nant-y-Gwyddon landfill site, the 22 "control" wards used in the study, Rhondda Cynon Taf Unitary Authority (in which the landfill site is situated) and Wales as a whole (Table 1). Data on spontaneous fetal losses were excluded from the analysis as miscarriages were not included in Fielder's study. Our data suggest a slightly higher overall prevalence of cases of congenital anomaly among babies / fetuses of women living in wards surrounding the landfill site both compared to the control wards and to Rhondda Cynon Taf Unitary Authority. Nevertheless, the percentage of babies / fetuses affected by congenital anomaly in the wards surrounding the Nant-y-Gwyddon landfill site is no higher than that reported overall for Wales. None of the differences found reached statistical significance on Chi Square testing. The situation should become clearer as further years of data are collected. Fielder's study refers to both actual cases of congenital anomaly and anomaly rates without clearly differentiating between these terms. CARIS defines a case as a baby or fetus and an anomaly as the defects detected in the case. Thus, the numbers of cases and numbers of anomalies in a given population may be very different. In Fielder's study, based on ONS data, this difference may not be significant as ONS reports 1.2 anomalies per case. 4 However, in 1998 CARIS reported an average of 2.5 anomalies per case for Wales. 3 In the future it will be important to distinguish between numbers of cases and numbers of anomalies so that equivalent comparisons can be ensured. Yours sincerely, Judith Greenacre - Consultant in Public Health Medicine Margery Morgan - Consultant Obstetrician & Gynaecologist David Tucker - CARIS project manager CARIS Office, Level 3 West wing, Singleton Hospital, Swansea. SA2 8QA dave.tucker@swansea-tr.wales.nhs.uk 1. Fielder HMP, Poon King CM Palmer SR Moss N Coleman G. Assessment of impact on health of residents living near the Nant-y-Gwyddon landfill site: retrospective analysis. BMJ 2000 320:19-22 2. Dolk H. Commentary: Impact on health needs assessing from different angles. BMJ 2000 320:23 3. Congenital Anomaly Register and Information Service for Wales. Annual Report 1998. CARIS 4. Congenital Anomaly Statistics 1997 (MB3 No 12). ONS Table 1: Total births and numbers of babies / fetuses reported to be affected by congenital anomalies in Wales, Rhondda Cynon Taf Unitary Authority, wards surrounding the Nant-y-Gwyddon landfill site and 22 control wards in 1998.
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Area No considered Nos of cases of congenital
abnormality reported to CARIS*
A B C D E F % affected
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Wales 33610 33798 188 609 24 821 2.43%
Rhondda Cynon Taf 2824 2840 16 39 1 56 1.97%
Nant-y-Gwyddon wards 253 256 3 3 0 6 2.34%
22 control wards 1349 1356 7 17 0 24 1.77%
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*Excluding spontaneous fetal losses.
A=Total births reported by ONS.
B=Total births+terminations with congenital abnormality.
C=Terminations of pregnancy.
D=Livebirths.
E=Stillbirths.
F=Total cases.
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