New Delhi: A congenital heart defect (CHD) is a structural abnormality in the heart or the major blood vessels near the heart that is present at birth. These defects can involve the valves, or blood vessels or the heart muscles per se, affecting the heart’s ability to contract or function properly. CHDs range in severity from minor defects that may not require treatment to life-threatening conditions that require immediate medical intervention
CHDs are among the most prevalent birth defects worldwide, affecting approximately 1 per cent of live births. The exact cause of CHDs is often unknown, but they can result from genetic factors, maternal health conditions, environmental factors, or a combination of these factors.
Maternal diabetes, particularly gestational and pre-existing diabetes, has been identified as a significant risk factor for CHDs.
Various types of Diabetes Mellitus include Type 1 diabetes mellitus (T1DM) which was previously called as Insulin dependent diabetes mellitus, Type 2 diabetes mellitus (T2DM, which is strongly associated with lifestyle factors such as obesity, physical inactivity, and poor dietary habits), gestational diabetes mellitus (GDM) that occurs during pregnancy and is characterised by high blood sugar levels that develop or are first recognised during pregnancy. It is thought to result from hormonal changes and increased insulin resistance during pregnancy. Both T2DM and GDM can affect the fetus and increase the risk of congenital defects including CHDs.
GDM usually resolves following the child birth but it can be associated with various complications like large baby – posing higher risk for birth injuries, breathing difficulty called respiratory distress syndrome because of surfactant destruction, jitteriness, hypoglycemia, neonatal jaundice, higher incidence of birth defects including congenital heart defects.
Fortunately GDM is a modifiable risk factor for CHDs thereby providing enough opportunity to try and prevent life threatening defects to be left to diagnose immediately after birth.
There is enough evidence linking the association between GDM and CHDs. Some of the proposed underlying mechanisms for the above risk include hyperglycemia-induced oxidative stress and DNA damage, altered cardiac development due to maternal hyperglycemia and disruption of fetal cardiac gene expression.
Other risk factors associated with GDM like obesity and hypertension can exacerbate the risk of congenital defects. Antenatal screening for all mothers with GDM along with fetal echo for screening of heart defects would reduce the incidence and helps in making an early diagnosis.
Similarly, early detection of GDM and optimal control of blood glucose which can be achieved with collaborative work of obstetricians, endocrinologists, physicians, fetal medicine experts and neonatologists can help in early detection and timely management of CHDs and thereby improve overall outcomes.
To summarise, CHDs are one of the commonest birth defects and can pose a significant problem not just in immediate neonatal period but also a major long term health problem. Maternal diabetes, both T2DM and GDM, is a major cause of concern but modifiable risk factor for CHDs. Tight blood glucose control, immediately before pregnancy and during pregnancy along with good perinatal care are essential reducing the risk of congenital anomalies and improve the outcomes for both mother and baby as well.
