Introduction
Congenital anomalies are one of the leading causes of neonatal morbidity and mortality globally. The greatest burden of disease is faced by those in low/middle-income countries (LMICs), as 94% of congenital anomalies occur in these regions.1 Congenital anomalies comprise 9% of the total global burden of surgical disease and account for 57.7 million disability-adjusted life years lost annually across the globe.2 Recent estimates suggest that approximately 303 000 neonates die annually from congenital anomalies before reaching just 4 weeks of age.3 However, many experts believe that this is an underestimate, due to a lack of congenital anomaly registries and some neonates dying without a diagnosis or inclusion within current statistics.
The WHO defines congenital anomalies as either structural or functional abnormalities which occur during intrauterine development.3 Structural anomalies are physical abnormalities that occur when the organs or skeletal structure are improperly formed. These can often be detected on ultrasound antenatally and are the focus of this review. Some common structural congenital anomalies include heart defects, cleft lip and palate, neural tube defects, limb deformities and abdominal wall defects. Many structural anomalies require immediate surgical intervention at birth to avoid death or preventable disability. In such cases, antenatal diagnosis permits delivery at a centre where the appropriate surgical care can be provided on delivery, for example, gastroschisis where the intestines protrude through a hole in the abdominal wall at birth. In high-income countries (HICs), where the majority of cases are antenatally diagnosed, mortality is less than 5%, while in many LMICs, with limited antenatal diagnosis, the mortality rate can be as high as 100%.4–6
The use of ultrasound technology in LMICs has significantly increased in recent years, as ultrasound machines have become more compact, transportable and affordable.7 Yet, a great number of congenital anomalies that can be detected antenatally via ultrasound go undiagnosed. Factors identified as barriers to effective antenatal ultrasound include limited training, equipment shortages, faulty ultrasound equipment and lack of maintenance services.7 In recent years, higher global priority has been given to neonatal health. Sustainable development goal 3.2 aims to end all preventable under-5 deaths and reduce neonatal mortality in every country to 12 per 1000 live births.8 In 2010, the WHO released the 63rd World Health Assembly Report on Birth Defects, recommending ‘prevention whenever possible, to implement screening programs and to provide care and ongoing support to children with birth defects and their families’.9
To develop a better understanding of antenatal ultrasound provision in LMICs, this study aimed to systematically investigate the availability and effectiveness of antenatal ultrasound in the diagnosis of structural congenital anomalies in LMICs. It further aimed to evaluate the effects of antenatal ultrasound diagnosis on mortality and morbidity outcomes, termination rates and referral for further antenatal care and management planning. Additionally, it assessed the level of training of ultrasonographers undertaking antenatal scans and relevant antenatal ultrasound policies in LMICs. This information is vital to help clarify the existing disparities in antenatal ultrasound provision and the potential benefits for improved health outcomes.