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Watch the sugar and cradle the baby’s heart

Watch the sugar and cradle the baby’s heart

Mothers with uncontrolled blood sugar levels during conception and early pregnancy are at risk of giving birth to babies with congenital heart diseases

diabetes during pregnancy can put a mother at higher risk of delivering a baby with congenital heart defect.

Thirty-seven-year-old Sonam Shah (name changed to protect privacy) from Bengaluru delivered a baby boy in September 2022. But unfortunately, the baby was diagnosed with a congenital heart defect called ventricular septal defect (VSD). One of the main reasons for it, according to experts, is her uncontrolled diabetes during pregnancy.

Studies have shown that women with diabetes before pregnancy are four to five times more at risk of having a baby with congenital heart disease (CHD). Sonam’s HbA1c (blood sugar) levels were at eight per cent when her pregnancy was confirmed. She was started on insulin immediately.

Dr Mokshadayini S, her consultant obstetrician and consultant reproductive genomics, MedGenome, recalls, “She delivered a boy of 3.5 kg after 39 weeks of gestation. An ECHO was done after birth, which confirmed VSD and it didn’t require any immediate intervention. The baby is healthy and is under follow-up with a paediatric cardiologist.”

Congenital heart defects associated with maternal diabetes

Babies of diabetic mothers are likely to have two kinds of cardiac problems – structural and functional, according to Dr Ashutosh Marwah, director, paediatric cardiology, Fortis Escorts Heart Institute, New Delhi.

“The functional defects include hypertrophic cardiomyopathy (HCM) which is due to the excess glycogen deposition, a type of carbohydrate in the cardiac muscles; the heart gets stiff. But the body will utilise glycogen and the heart will normalise usually within four to six weeks,” he says.

Structural defects like truncus arteriosus classified as conotruncal abnormalities (group of CHD involving great vessels and outflow tracts of the heart) are more severe.

The most common congenital heart conditions are:

  • Ventricular septal defects (abnormal formation of the wall between the right and left ventricle)
  • Transposition of great arteries (two main arteries leaving the heart are transposed)
  • Hypertrophic cardiomyopathy (thickening of heart muscles)
  • Patent ductus arteriosus (persistent opening between the two major blood vessels from the heart)
  • Atrial septal defects (hole between the upper chambers of the heart)
  • Tetralogy of Fallot (combination of four heart defects)
  • Truncus arteriosus (when the blood vessel from the heart fails to separate completely during development)
  • Pulmonary atresia (improper blood flow to lungs)

Most CHD conditions can be corrected except for severe conditions like hypoplastic left heart syndrome (the left side of the heart does not form properly), says Dr Marwah. The child needs to have annual check-ups in such a case. “Some can have problems of rhythms or may require valve replacements later in their lives,” he says.

The symptoms of CHD vary based on the severity of the defect. It could include symptoms like fast breathing, poor weight gain, chest infections and blueness of nails and lips. Dr Marwah also adds that milder CHD versions are overtly asymptomatic and are detected only during evaluation.

A 2020 study titled, ‘Maternal Obesity and Diabetes Mellitus as Risk Factors for Congenital Heart Disease in the Offspring’, published in the Journal of American Heart Association cites a prenatal care meta-analysis stating a 75 per cent reduction in risk of anatomical malformations in offspring, including congenital heart disease due to maternal diabetes management.

Dr Mokshadayini says cardiovascular malformations are the most common malformations in insulin-dependent diabetic mothers and about 2.5-10 times higher than observed in normal pregnancies. “Incidence of complications is 3.4 per cent in those with HbA1c levels lower than 8.5 per cent, and 22.4 per cent in those with HbA1c levels higher than 8.5 per cent,” she says.

Dr Suman Lal, associate director, obstetrics and gynaecology, Max Hospital, Gurgaon, says that if the sugar levels are not controlled during early pregnancy, the baby will be exposed to transient hyperinsulinism (unregulated insulin secretion from pancreatic beta cells) that can cause hypertrophic cardiomyopathy.

Congenital heart defects

High blood sugar levels can lead to alterations in the biochemistry and affect genes responsible for the normal development of the baby. The severity of foetal cardiac damage depends on the degree and duration of hyperglycaemia and hyperketonaemia (high levels of ketones in the blood).

Dr Anantharaman R, consultant endocrinologist and diabetologist, Magna Centres for Obesity Diabetes and Endocrinology, Bengaluru, says, “High blood glucose level can lead to more reactive oxygen species (that can cause damage to DNA, RNA and proteins) and endothelial dysfunction (a type of coronary artery disease that leads to narrowing of arteries) in the foetus. There can be a production of advanced glycation end products (AGEs: harmful compounds formed when proteins or fat get mixed with glucose in the blood), which interferes with embryogenesis (a process where the embryo develops into a foetus).”

Dr Mokshadayini says studies show that uncontrolled diabetes can thus affect ‘foetal programming’. Foetal programming (or conditioning) is the process that occurs during the critical period of pregnancy which can have detrimental effects on the foetus and the later life of the baby. “Foetal programming is suspected to be involved in the development of cardiometabolic disorders, such as elevated blood pressure, coronary heart diseases or diabetes mellitus notably through epigenetic mechanisms (cells controlling the gene activity without altering the DNA sequence),” she says.

Gestational diabetes and congenital heart defects

The higher the HbA1c levels, the higher the risk of CHD but most defects can be detected through scans during pregnancy. Dr Suman says, “Some defects can be detected during the scan at 18 to 19 weeks of pregnancy. But at that time, the heart is not developed. At 23 to 24 weeks of pregnancy, a foetal ECHO is done, which picks most abnormalities. If any gross abnormality is noticed, we suggest termination of pregnancy,” she adds.

The compromised state of the heart may affect the foetal heart rate. “There are more chances of premature delivery and stillbirths. If we find any abnormality in the heart rate, we deliver the baby sooner. The pregnancy is continued to 40 weeks if the sugar levels are fine,” she says.

Pregnancy and diabetes risks

Maternal diabetes is managed through insulin or diabetes medication that is safe to take during pregnancy. Dr Ananthraman says, “Type 1 diabetics are more at risk of giving birth to a baby with malformations as it is difficult to control glucose levels, compared to type 2 diabetes.”

Gestational diabetes does not usually lead to any malformations in the baby, say experts. However, it may lead to overgrowth of the foetus, causing difficulty in delivery.

Experts suggest the following to control blood sugar:

  • Include less than 50 per cent of carbs in your diet
  • Work on portion control if you are overeating
  • Add more protein to your diet
  • Avoid processed foods like biscuits, juices and snacks
  • Do some light intense workouts, as advised by the doctor

Dr Anantharaman says, “Most maternal diabetes cases are easy to manage. What is required are self-monitoring, awareness and lifestyle changes before and during conception.”

Hole in heart by birth

The presence of CHD could affect the lifestyle and mental health of the child. Dr Marwah says, “The child will have a scar on his chest and is often reminded by his family or friends about his heart condition. But otherwise, they can lead normal, socially productive lives.”


Studies have shown that women with uncontrolled diabetes before pregnancy are four to five times more at risk of having a baby with congenital heart disease. The defects can be diagnosed during the foetal ECHO at 24 weeks of pregnancy. The symptoms of CHD vary based on the severity of the defect and include fast breathing, poor weight gain, chest infections, and blueness of nails and lips. Some babies can be asymptomatic at birth and a heart condition may be only detected when they are evaluated by a doctor using a stethoscope. Most CHD conditions can be corrected but can affect the lifestyle, mental health and physical endurance of the child, as the child will require annual check-ups.

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