Introduction

Congenital heart diseases (CHD) contribute significantly to infant morbidity and mortality globally and this is especially more in the low- and middle-income countries (LMICs) where there is dire need for improvement in health services. A wide range of maternal, foetal, and neonatal risk factors influence the birth prevalence of CHD, including access to primary care, accurate neonatal examinations, rates of prenatal diagnosis, and pregnancy terminations, all of which vary geographically. ^1,2 Lack of wide availability of CHD screening and interventions during antenatal and postnatal periods also contribute to morbidity and early mortality, especially in the LMICs.³ In addition to prevalence and mortality rates, the rates of morbidity related to CHD, including developmental disability, and quality of life, are key to evaluating the burden of CHD.^4-6

An estimated 6% of babies worldwide are born with a congenital anomaly.⁷ It accounts for 7% of neonatal death and a staggering 25.3–38.8 million disability-adjusted life-years (DALYs) worldwide.^8-10  The World Health Organization’s (WHO) global burden of disease (GBD) study reports that anomalies rank 17th in causes of disease burden.(9) There is a report that African countries were most likely to have congenital anomalies in children under 5 years of age.¹¹ The Global Burden of Disease Study 2016 reported that higher rates of congenital anomalies were found among countries with poorer social and demographic indicators.¹² It has been estimated that more than 90% of severe congenital anomalies occur in the LMIC.^8,13 Liu et al,¹⁴ in 2015, reported that congenital anomaly was a significant cause of death in children under 5 years of age in countries with the highest under-5 mortality rates (e.g. Angola, Central African Republic, Chad, Mali, Nigeria, Sierra Leone, and Somalia). In these countries, polio, malaria, and diarrhoea are the three leading causes of death under five. Research indicates that heart abnormalities affect at least 1% - 2% of all newborns each year worldwide making it the most common birth   defects. ^10,15-17 Not all CHD patients are diagnosed early, making it difficult to determine the true prevalence. CHD affects both high-income and low-income countries, with associated impact on health systems with varying resources and scope. While the global prevalence of birth defects has remained stable over time, the prevalence of CHD has nearly doubled since the 1970s, likely due to changes in the detection and availability of ultrasound.¹⁸ An estimate from Canada suggested a global prevalence of 13.1 per 1000 children and 6.1 per 1000 adults.¹⁹ Their data also suggest that CHD prevalence increased from 2000 to 2010 by 11% in children and 57% in adults. An increasing number of CHD patients now survive into their 30s and beyond due to improvement in medical care and this may have contributed to the higher prevalence among older persons. Asia has the highest overall CHD rate (9.3 per 1000 live births), much higher than Europe (8.2 per 1000 live births) and North America (6.9 per 1000 live births). Major CHD is said to occur in 1.1 per 1000 live births.²⁰ Disparate genetic and environmental risks, including inequalities in social determinants of health, may play a dominant role in the observed geographic discrepancy in CHD prevalence. Children born in low-income areas of Canada have been reported to have a significantly higher incidence of CHD despite the universal access to health care.²¹

Tremendous advances in diagnosis and management of complex CHD have been made in developed regions of the world, but not the same in most LMICs. ^8,22 There are an estimated 500,000 children born in Africa with CHD each year with a major proportion of this in sub-Saharan Africa. The vast majority of these children receive suboptimal or no care at all. The Global Burden of Disease Study estimated that 80% of deaths from non-communicable diseases, including CHD, now occur in LMICs. CHDs were reported in 122 (9.3%) of the 1312 patients (aged 9 days to 35 years) with abnormal echocardiograms from northern Nigeria.²³ This further stresses the burden of this condition in the LMICs and the need to establish measures for early diagnosis and care.

Aetiology/Risk Factors for Congenital Heart Diseases

The aetiology of congenital heart disease (CHD) has been considered to be multifactorial, due to both genetic predisposition and environmental influences,^24-27 profoundly influenced by conditions in foetal and early life. It is generally known that exposure to pharmaceuticals, such as antiepileptic drugs, lithium, and alcohol, is linked to a higher risk of congenital heart disease (CHD) in the developing foetus. Environmental exposures may have a role in the development of CHD, which is a growing source of worry. Observational studies have shown a higher incidence of transposition of great arteries in babies of mothers exposed to herbicides and a higher incidence of ventricular septal abnormalities in parents exposed to pesticides.^2,28Additionally, higher incidence of CHD has been linked to maternal cigarette smoking  in  early pregnancy,  and  some  studies  have, after controlling for  socioeconomic  status,  linked  ambient  air  pollution  to  CHD.^29,30 In  addition  to  maternal  environmental  exposures,  associations between maternal nutritional status and the development of  CHD  in  offspring  have been  observed. Reduced rates of CHD, particularly transposition of the major arteries, have been linked to the introduction of folate to lower the prevalence of neural tube abnormalities.³¹ The availability of foods containing folate may be reduced in low socioeconomic status areas, and this may lead to inadequate folate levels to avoid birth abnormalities. Furthermore, interactions between maternal lifestyle elements that affect the metabolism of folate, like obesity and carrier rates for specific genetic variants, have been linked to higher incidences of CHD.³² Similarly, studies have documented associations between maternal hyperglycaemia and hyperlipidaemia and increased risk of CHD.³³ Maternal diabetes is strongly associated with certain cardiac defects and the increasing  prevalence  of  glucose  intolerance  seen  with  maternal obesity and elevated body mass index is linked to socioeconomic status.²⁴ The presence of some maternal infectious diseases such as syphilis and rubella has been implicated in the occurrence of CHD.

Indications For Screening for Heart Malformations

Every pregnant woman should as part of standard obstetric care have her baby screened for the presence of structural problems with the heart. Majority of the congenital anomalies occur in foetuses born to parents with no obvious risk factors.^6,34Screening for foetal cardiac abnormalities should begin during the routine first trimester scan when the CRL measures between 45mm to 84mm and this should assess the normal position of the heart as a minimum.³⁵ More detailed assessment of the heart should be done during the 2nd trimester anatomy scan. Fetal echocardiography is now widely used to detect, characterise, and help manage congenital cardiac malformations. Indications for performing a fetal echocardiogram have been formulated and were described in an  American  Heart  Association  scientific  statement.^26,36 Particular risk factors for CHDs, such as those linked to mother's health like diabetes mellitus and autoimmune diseases; maternal exposure to drugs or toxic substances; disorders of umbilical-placental development such as single umbilical artery; and known presumed or possible heritable conditions should warrant further evaluation with a foetal echocardiogram. Foetal echocardiograms should be performed in pregnancies if the mother, father, or sibling has a congenital heart abnormality.

While foetal echocardiogram may still be considered when there is a history of CHD in a second-degree family member, it is not recommended with history of CHD in a third-degree or more distant relative. In a like manner, where there is a history heritable condition in a first-degree family relative that is associated with a risk of heart defects, e.g., Noonan Syndrome, even if the affected relative does not have a heart defect, foetal echocardiogram should be carried out. Where a non-cardiac abnormality suggestive of a possible genetic syndrome, teratogen, or malformation sequence have been detected on scan, it is recommended that a foetal echocardiogram is performed in order to rule out or diagnose co-existing heart abnormalities. The likelihood of a concomitant CHD in a foetus with another anomaly varies, but structural abnormalities of the kidney, gastrointestinal tract, abdomen, craniofacial structures, or limbs, as well as microcephaly, hydrocephaly, agenesis of the corpus callosum, or other abnormalities of the central nervous system, should prompt referral for evaluation with a foetal echocardiogram.³⁷ Additionally, even if cffDNA screening does not reveal a chromosomal abnormality, features like increased nuchal translucency or unexplained foetal growth delay are indicators for performing a fetal echocardiogram because they are linked to a significant risk of congenital cardiac abnormalities.^38,39 There are evidence reporting the increasing incidence of major structural abnormalities with increasing nuchal translucency in the presence of normal karyotype.⁴⁰

Challenges Of CHD Screening in The LMICs

CHD screening and diagnosis in the LMICs have been bedevilled by a lot of challenges. Advances in technology have resulted in the improvement of medical diagnostic equipment and development of new ones. One of the areas where these advances are marked is in the development of ultrasound machines. There is wide availability of high-resolution machines which has brought about a significant improvement in the diagnosis of foetal cardiac conditions. However, these machines are not widely available in the LMICs which has limited the level of involvement in CHD screening and diagnosis.^41,42 The output of an ultrasound machine is as good as the skills of the operator. Regardless of the quality of the equipment, if there are no requisite skills to operate it, it is as good as no equipment. A study in Nigeria reported a sensitivity of ultrasound in detecting abnormality to be as high as 93% in a skilled hand. Unfortunately, there are relatively few persons who are adequately trained to make these diagnoses in LMICs.^41,43 The often absence of policies and protocols has resulted in huge variation in practices. Policies and protocols ensure that there is consistency in the process and structure of the screening thus preventing chaos. It ensures a safer process and better-quality services to the patients. Unfortunately, the often lack of these in LMICs means that routine CHD screening is not incorporated into the routine obstetric practices and results in variation of practices even within the same country. 

Enshrined in the daily existence of individuals and groups of individuals is their belief system. This forms what they are and determines what they accept or not. The sociocultural culture of the people influences their decision to utilise a particular health service. Where there is conflict between the beliefs of the woman and the services provided, utilisation of such services will be limited.^41,44 This can sometimes pose a challenge in the effective utilisation of the available screening facilities. Some studies have reported that women do not access health care either because the facility is not available or because of their inherent beliefs. This stresses the role of prenatal education in the utilisation of healthcare facilities. It is important that women are adequately and appropriately educated in order to help them understand the purpose of the screening and encourage them to utilise it. There are studies reporting a linear relationship between prenatal education and maternity services utilisation.⁴⁵ The relatively high ratio of women to available maternity services in some LMICs has resulted in poor knowledge of CHD screening among a significant proportion of women.⁴¹ Some authors have reported the use of mass media such as radio and television to educate and sensitise the people on important maternity health issues.⁴⁶ This may come handy in enlightening the women on CHD screening. 

The high prevalence of CHD suggests that leaving the role of screening and diagnosis for the tertiary health facilities may be a daunting task which will never be effective or actually achieved. There is therefore the need for involvement of all levels of health care, from primary level to tertiary level. At the primary level, screening of women to identify those at high risk of having a baby with congenital heart diseases can be done and such women referred to the secondary or tertiary facilities as appropriate for further counselling, screening and diagnosis. Unfortunately, this structure is often epileptic or non-functional in a lot of LMICs which poses a huge challenge to the quality of health care services and CHD screening in particular. One of the WHO criteria for screening is the availability of facilities for diagnosis and treatment.⁴⁷ The ability to make complicated fetal diagnosis is a waste of time if there is no clinician or facility to treat the baby. The WHO has estimated that over 50% of disability-adjusted life years (DALYs) lost each year due to congenital anomalies could be prevented with prompt surgery or other treatment.⁷ This is also largely unavailable in the LMICs which has further resulted in the wide disparities between the high income countries (HICs)  and the LMICs. Underpinning the challenges of CHD screening and diagnosis in the LMICs is the lack of political commitment. At the heart of Africa’s fragile health systems is the perennial failure by governments to prioritise health and allocate it adequate resources. African heads of states and governments under the African Union (AU), in April 2001 in what is known as the ‘Abuja Declaration’, made a pledge to allocate at least 15 percent of their annual budgets to the health sector in order to meet the inadequacies in the health systems.⁴⁸ Only very few of the AU member countries have met this commitment. This is the case with a lot of the LMICs which poses a huge challenge in the availability and training of skilled manpower to offer the screening and availability of facilities for diagnosis and treatment of CHD. Data from global health expenditure database revealed that the LMICs spend only about 5% of their GDP on health.⁴⁹

Establishing CHD care

Establishing CHD care should cover all stages of pregnancy, beginning from the preconception period and continuing to postnatal. At the preconception period, there is the need to identify women at the higher risk and identify risk factors in them. Measures should be taken to control the modifiable factors prior to pregnancy as this will reduce their risk of having a baby with CHD. These can involve dietary advice including supplementation with essential vitamins, cessation of substance use including smoking and weight reduction programme. Those with non-modifiable factors should be referred early enough to the appropriate specialist so that measures are taken to reduce their chance of having a baby with CHD and for early diagnosis of foetuses with heart diseases. There is therefore the need to establish preconception clinics where this care can be rendered, and this should ideally be at the primary care level. This again stresses the need to ensure that the various levels of health care are functioning.  

The role of early prenatal diagnosis of CHD cannot be overemphasised. It allows for improved counselling of the patients on the cardiac condition at a time when the couple can make an informed decision to either continue the pregnancy or stop it. It also guides the timing, mode and location of delivery. There may be a need for elective delivery at a time when there can be an appropriate specialist on ground to look after the newborn baby and this can sometimes be immediate surgery. In situations where the appropriate care the baby will require at birth is unavailable at the facility where the woman is having her antenatal care, transfer to another facility becomes important. This is only possible when there has been prenatal diagnosis of the condition. Prenatal diagnosis will also allow appropriate planning and consultation between the cardiologist and the neonatologist. It is usually important to plan consultation with the paediatric cardiologist during the antenatal period. This will offer the couple the opportunity to receive more information on the outlook of the condition as well as the kind of care that the baby will have after care. This stresses the role of a multidisciplinary team in the care of babies with CHD as it is impossible for the foetal medicine specialist or the obstetrician to deliver a quality CHD care alone. This can help the psychological wellbeing of the couple as well as involve them in the care of the baby.

Currently a lot of diagnosis of CHD in the LMICs are done postnatally either when they are unwell or even at postmortem. This is largely due to the nonavailability of effective prenatal diagnosis services. In addition, prenatal diagnosis cannot identify 100% of babies with CHD even in the best hands. A lot of these diagnoses can be made at birth or during infancy through a comprehensive newborn and infant physical examination. There is therefore the need to invest in the training of midwives and nurses to be able to identify these signs so that appropriate referral can be made. The role of inter-specialty and inter-facilities collaboration is again emphasised in the treatment of the newborn with CHD. There should be establishment of specialised paediatric cardiac centres where these babies can be cared for. Supporting couples with a baby with CHD is very important. Diagnosis of CHD can be a source of significant mental health issues in the couple. Therefore, providing them with adequate psychological support regardless of their decision to continue the pregnancy or not is important. The need for referral to a specialised counsellor or psychologist should be identified early enough. 

Conclusion and Recommendations

CHDs represent one of the main causes of the total burden of disease and are associated with significant neonatal and infant death. The LMICs house the major burden of congenital anomalies, CHDs inclusive, yet there is dearth in the diagnosis and treatment of these conditions. There is urgent call for improved health care in the LMICs.

If effective foetal cardiac anomalies screening and diagnosis programme is to be established, there must be political commitment. Issues of health should be given appropriate attention in the national budget and expenditure. The Abuja Declaration target of at least 15% of their annual budget to improve the health sector by the AU states will need to be executed.⁴⁸

Considering the fact that no progress can be made in the diagnosis & treatment of CHDs without the requisite facilities, appropriate facilities should be made available. There should be provision of ultrasound machines to facilitate this. There should be investment in training of obstetricians, midwives and sonographers. The midwives and sonographers should be trained on basic cardiac scans, they can in turn make referrals to the foetal medicine specialist for confirmation and detail scanning. This will help to ensure that the services are extended to the women in the rural areas. This has been found to be effective in the high-income countries and in LMICs where it has been tried.⁵⁰

It is irrelevant possessing the best skills and having the most powerful diagnostic and treatment facilities if the women cannot afford it. Therefore, low-cost policy for the provision of foetal imaging services should be developed in the LMICs. There are reports of good outcomes from countries where low-cost policy has been tried. Also, providing health insurance for the people is a way to improve accessibility to health care services. 

Establishing minimum standards in the training and practice of obstetric scans is a prerequisite for provision of quality services. Appropriate care cannot be guaranteed in situations where Obstetric ultrasound practitioners do different things with no minimum requirements. There is, therefore, the need to develop standards in the training of US practitioners. 

The role of established policies/protocols for prenatal screening and diagnosis cannot be overemphasised. It ensures that standards are maintained and that there is uniformity in the services that are rendered. This plays a role in fostering delivery of quality services.

There cannot be effective and efficient congenital cardiac anomalies services without the involvement of multidisciplinary teams. The management of pregnancies and babies with diagnosed heart defects is complex. There should be inter-facilities and inter-specialties collaboration to ensure that the appropriate care is delivered.

A huge shortfall still exists in data relating to congenital anomalies including CHD in the LMICs despite the huge burden of congenital anomalies. This is mainly due to non-presentation at health facilities, deficient diagnostic capacity, poor awareness, under-reporting and lack of registries for congenital anomalies.^51,52 The consequence of this is significant under-estimation of birth defects. There is therefore an urgent need to establish national registries where CHD are reported. This is important for research and auditing. It will promote the culture of documentation and reporting. It also will help to identify areas where CHD or certain types of CHD are predominant and hence public health measures to identify the prevalence risk factors in such areas with the aim of instituting an intervention to reduce rate.

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