Abstract
Congenital anomalies are amongst the leading causes of fetal and infant mortality and morbidity, yet are not consistently monitored within existing indicators used to assess the health and wellbeing of the New Zealand population. Routine monitoring of public health indicators assists with designing and evaluation of health strategies, priorities and policies, as well as measuring the impact and utilisation of health services and interventions.
This thesis sought to identify existing public health indicators for congenital anomalies in New Zealand, and assess whether these were comparable to international indicators. It also sought to identify international indicators not measured in New Zealand, and the potential for their adoption. From which, one was selected for a prevalence study to test the practicalities of implementation using existing administrative collections.
Six public health indicators for congenital anomalies were identified as being or having been monitored in New Zealand, and these were comparable to international indicators. Three international indicators were without a New Zealand equivalent, and only one, namely the indicator for “congenital anomalies typically requiring surgery”, showed potential for adoption, based on existing information within the New Zealand literature. This indicator was therefore selected for a prevalence study, which served as a means of testing the practicalities of implementing this indicator.
Methods
The prevalence of selected congenital anomalies typically requiring surgery in New Zealand was reported based on the EUROCAT (European network for the surveillance of congenital anomalies) definition for the period 2000–2011. The study utilised livebirth information held within the National Minimum Dataset and fetal death information from the National Mortality Collection. Prevalence was assessed in relation to time, and demographic risk factors, specifically maternal age, fetus/baby’s prioritised ethnicity, gestational age, and sex.
Results
In New Zealand, the prevalence of congenital anomalies typically requiring surgery was 4.1 per 1,000 births for 2000–2011, and a livebirth prevalence of 3.7 per 1,000 births. The temporal trend essentially remained stable over the period. Prevalence of congenital anomalies typically requiring surgery was significantly higher for male fetuses/babies, for premature births, for fetuses/babies born to women of either young or advanced maternal age, and significantly lower for fetuses/babies of Māori or Pacific ethnicities. Of the select anomalies encompassed within the indicator, only gastroschisis had a prevalence that was significantly higher in 2011 than in 2000.
Discussion
New Zealand has six congenital anomaly indicators comparable to international indicators; however, these indicators are inconsistently monitored by four organisations. This creates the potential for misrepresentation of prevalence, which can impact on the planning and provision of services, interventions, and public health policy. A congenital anomaly-specific framework would assist with rectifying these differences and ensure complete representation of prevalence. This thesis provides the foundations for such a framework, and identified an additional indicator that could be implemented in practice.
This thesis highlights the importance of reliable indicators for reporting the prevalence of congenital anomalies, particularly when used in conjunction with prevalence studies. Information on the prevalence of congenital anomalies serves to increase the visibility and awareness of congenital anomalies in New Zealand, particularly among health professionals, and aids the planning and evaluation of public health policy and services.