Congenital anomalies, also known as birth defects, are structural or functional abnormalities, including metabolic disorders, which are present at birth. Congenital anomalies are a diverse group of disorders of prenatal origin, which can be caused by single-gene defects, chromosomal disorders, multifactorial inheritance, environmental teratogens or micronutrient malnutrition.
This manual is intended to serve as a tool for the development, implementation and ongoing improvement of a congenital anomalies surveillance programme, particularly for countries with limited resources. The focus of the manual is on population-based and hospital-based surveillance programmes. Some countries might not find it feasible to begin with the development of a population-based programme. Therefore, the manual covers the methodology needed for the development of both population-based and hospital-based surveillance programmes. Further, although many births in predominantly low- and middle-income countries (LMICs) occur outside of hospitals, some countries with limited resources might choose to start with a hospital-based surveillance programme and expand it later into one that is population-based. Any country wishing to expand its current hospital-based programme into a population-based programme, or to begin the initial development of a population-based system, should find this manual helpful in reaching its goal.
This manual provides selected examples of congenital anomalies (see Appendix A). These anomalies are severe enough that many would probably be captured during the first few days following birth. While a number of the anomalies listed are external and easily identified by physical exam, others are internal and typically require more advanced diagnostic evaluations such as imaging. However, because of their severity and frequency, all these selected conditions have significant public health impact, and for some there is a potential for primary prevention.
Nevertheless, these are just suggestions; countries might choose to monitor a subset of these conditions or add other congenital anomalies to meet their needs. In particular, this manual will help the reader to:
- describe the purpose and importance of public health surveillance of congenital anomalies;
- describe the use of logic models for planning and evaluation of a surveillance programme;
- understand how to present data to policy-makers;
- identify an initial list of congenital anomalies to consider for monitoring;
- describe the tools needed to ascertain and code identified cases;
- describe the processes for managing and analysing data; and
- understand how to calculate the prevalence of congenital anomalies.
Surveillance of congenital anomalies should be ongoing and should involve a systematic review of birth outcomes to determine the presence of congenital anomalies. If countries have the capacity to collect information on known risk factors associated with congenital anomalies – such as maternal exposures (e.g. use of medications during the first trimester) – these could be included in a surveillance programme. Alternatively, a pregnancy registry or a case–control study might be implemented to allow for the collection of exposure data during pregnancy. This manual is intended to facilitate the collection of essential information for the purpose of assessing and tracking the burden of congenital anomalies. It must be noted that the manual does not present specific information on how to collect risk factor information or how to manage a neonate born with congenital anomalies.