Two to three percent of infants are born with a congential anomaly, but who's counting? A national survey of congenital anomalies in Canada

Introduction

The thalidomide tragedy, recognized in 1962,1 led to the development of congenital anomalies surveillance systems in many jurisdictions. Today, identifying potential teratogens is one of many important public health functions served by congenital anomalies surveillance.

Major congenital anomalies are detected in two to three percent of births every year in Canada,2 and surveillance systems offer a way of evaluating the impact of prevention strategies (e.g., food fortification with folic acid). The systems are also useful in hypotheses generation, in describing the epidemiology of specific anomalies and in identifying infants in need of special services or programs. Existing systems have also been used for follow-up studies of survival and economic impact.3-5

In Canada, the Canadian Congenital Anomalies Surveillance Network (CCASN) was established in 2002 by Health Canada (now the Public Health Agency of Canada [PHAC]) under the umbrella of the Canadian Perinatal Surveillance System (CPSS). The CCASN is made up of clinicians, academics and public health professionals from across the country and its goal is to enhance the quality of surveillance data. It achieves this by advising PHAC on strategies that encourage provinces/territories to develop surveillance systems where there are none, and by maintaining and enhancing existing surveillance systems.

In December 2004, the CCASN undertook a national survey of congenital anomalies surveillance systems across the country. The goal of the survey was to gain a better understanding of existing surveillance systems and to determine how best to fulfill the CCASN's mission of supporting the development and maintenance of those that are both population based and of high quality.

Methods

A list of 37 potential respondents was compiled, which included representatives from provincial/territorial ministries of health, reproductive care programs, maternal serum screening, medical genetics programs and university departments of medical genetics. A questionnaire, based on a similar survey conducted by Miller and Kirby6 in the United States, was modified and approved by the CCASN advisory group. The questionnaire asked respondents whether they conduct congenital anomalies surveillance, for what time periods congenital anomalies data are available, whether these data include prenatal diagnostic data, which coding/classification system is used, and how data were used in the previous year.

A survey package was mailed, which included a stamped, return envelope. Two reminders were sent following the original mailing, after two and four weeks, respectively.

Results

The response rate to the survey was 76 percent (28/37). A breakdown by type of respondent is provided in Table 1 .

According to the responses, ten surveillance systems in eight provinces/territories collect congenital anomalies data. Four reproductive care programs (RCPs), three maternal serum screening/medical genetics programs and three provincial/territorial ministries of health operate surveillance systems.

The surveillance systems employ multiple sources of data, with the exception of the Ontario RCP, which uses only hospital records, and Yukon's Fetal Alcohol Spectrum Disorder (FASD) registry, which relies only on physician reports.

Seven of the ten surveillance systems collect data on all major birth defects, while three are more limited in the anomalies they monitor. The Yukon registry collects data on FASD, Newfoundland and Labrador's Medical Genetics Program collects data on neural tube defects (NTDs), and the Ontario Maternal Serum Screening Program focuses on NTDs, trisomies 18 and 21 and other cytogenetic and ultrasound abnormalities. Reproductive care programs, maternal serum screening programs and the medical genetics programs gather data until discharge from hospital or shortly thereafter. This is unlike the surveillance systems run by provincial and territorial Ministries of Health (i.e., Alberta, Yukon and British Columbia) , which capture data on infants up to one year of age, up to school age, and up to 19 years of age, respectively.

Respondents were asked to list the ways that they had used congenital anomalies data in the previous year. Eight (80 percent) replied that they conducted routine statistical monitoring, five (50 percent) used the data for epidemiological studies, and three (30 percent) used the data for monitoring outbreaks and cluster investigation. Other uses of the data included identifying cases for other epidemiological studies, evaluating public health programs and identifying individuals for referral to specialized services.

Further details on the surveillance systems are presented in Table 2.

Discussion

At the time of this survey, seven provinces and one territory had congenital anomalies surveillance systems. However, variations in coding, outcomes captured and case ascertainment make it difficult to compare rates across the country.

The ability to compare numbers and rates across provinces and territories is valuable, especially in regards to congenital anomalies. When rare events are studied, the sample size must often be increased to beyond that which is captured by one province or territory. If a new teratogen appears, its effects may be more rapidly detected if comparisons can be made across several jurisdictions.

A national surveillance system, the Canadian Congenital Anomalies Surveillance System (CCASS), does exist. This is the only population-based surveillance system in Canada which provides national data on congenital anomalies. However, it has several limitations that hinder its usefulness. CCASS relies primarily on hospital separations to calculate congenital anomaly rates. This reliance on administrative databases results in issues with timeliness and representativity (i.e., prenatal diagnoses of congenital anomalies that result in a termination of pregnancy are not captured). As well, key data elements are not available, such as the gestational age of the infant.

Major congenital anomalies are a leading cause of death in infants,2 and create a considerable emotional and economic burden for families and society.7"8 Surveillance systems make vital contributions to our knowledge of causative factors and to the evaluation of preventive measures.

Congenital anomalies surveillance is important to public health and should be promoted within all provinces and territories. The Canadian Congenital Anomalies Surveillance Network is taking the lead by working to develop guidelines for coding, a list of suggested congenital anomalies that should be captured, and recommended data collection practices.

A review of existing case definitions has already begun and preliminary recommendations have been developed. Once finalized, these guidelines and recommendations will be distributed to provincial and territorial representatives, and posted on the CCASN Web site. (http://www.phac-aspc. gc.ca/ccasn-rcsac/index.html)

Acknowledgements

We would like to thank all of our survey respondents for providing us with the information on their congenital anomalies registries and surveillance systems.

References

References

1. Speirs AL. Thalidomide and congenital abnormalities. Lancet. 1962 Feb 10;1:303305.

2. Health Canada. Canadian perinatal health report, 2003. Ottawa: Minister of Public Works and Government Services Canada, 2003.

3. Edmonds LD, Layde PM, James LM, Flynt JW, Erickson JD, Oakley GP Jr. Congenital malformations surveillance: two American systems. Int J Epidemiol. 1981 Sep;10(3): 247-52.

4. Cordero JF. Registries of birth defects and genetic diseases. Pediatr Clin North Am. 1992 Feb;39(l): 65-77.

5. Lechat MF, DoIk H. Registries of congenital anomalies: EUROCAT. Environ Health Perspect. 1993 JuklOl Suppl 2:153-7.

6. Miller LA, Kirby RS. Neural tube defects surveillance: a national survey. Teratology. 2000 Jan-Feb;61(l-2):28-32.

7. Hunfeld JA, Tempels A, Passchier J, Hazebroek FW, Tibboel D. Brief report: parental burden and grief one year' after the birth of a child with a congenital anomaly. J Pediatr Psychol. 1999 Dec;24(6):515-20.

8. Waitzman NJ, Romano PS, Scheffler RM. Estimates of the economic costs of birth defects. Inquiry. 1994 Summer;31(2):188205.