High blood sugar in pregnancy often stems from childhood diet, says study: How diabetes risk passes silently from under-fed mothers to children

The findings challenge the conventional classification of gestational diabetes mellitus (GDM) as a condition limited to pregnancy.

In 1993, Sonabai, a young woman from a village in Pune district, spent her days doing physically demanding work, washing farm animals, fetching water from the well and cooking for her family. Despite the labour, her diet was poor. Years of undernutrition quietly pushed up her blood sugar levels by impairing the pancreas, causing insulin deficiency even without obesity. At 23, she gave birth to her daughter, Maina, who grew up on fried and processed foods at home and potato chips in school meals. By age six, her blood sugar levels were already elevated. When she became a mother at 18 in 2020, she did not know that five years later her daughter would develop severe glucose intolerance.

Both Sonabai and Maina are part of a landmark Pune Maternal Nutrition Study study that began in 1993 in six villages in Pune district to understand how diabetes evolves over a lifetime in Indians. Now, using data from three decades ago, researchers from KEM Hospital and Research Centre have found that high blood sugar during pregnancy is not just related to pregnancy hormones, which make women resistant to insulin. It had to do with elevated glucose levels since their childhood, largely due to an imbalanced diet and malnutrition or undernutrition-induced prediabetes.

“Our findings suggest that high blood glucose in pregnancy is not a new condition caused by pregnancy but part of a life-long pattern,” says Dr Chittaranjan Yajnik, lead author of the study and founder director of the Diabetes Unit at KEM Hospital Research.

Between 1994 and 1996, approximately 800 women chosen for the study delivered babies. During this period, both mothers and children were monitored continuously for disease risks, including serial glucose tolerance tests. Earlier findings showed that 28 per cent of children had prediabetes at age 18.

At 18, Maina, who was born small at 2.5 kg, showed low to mild glucose intolerance. However, during pregnancy she developed gestational diabetes. Managed through dietary changes and lifestyle modification, including reducing processed foods, she delivered a 2.75 kg baby in 2020. By age five, Maina’s daughter had already progressed to severe glucose intolerance, placing her at strong risk of developing diabetes in the future.

“Our earlier findings showed that this tendency towards diabetes was linked to poor growth in the mother’s womb and high blood sugar levels in the parents. If one is born small, his/her system is unable to tolerate the stress of modern lifestyle rapid development in later years which increases the risk of diseases like diabetes, blood pressure and heart diseases,” Dr Yajnik explains.

This supports the Developmental Origins of Health and Disease (DOHAD) theory, which says that poor foetal nutrition programmes the body for insulin resistance. So, when nutrients become plentiful after birth, they potentially lead to diabetes. This metabolic adaptation, combined with potential genetic factors and rapid weight gain post-birth, increases future diabetes. “Improving the health of young girls will help reduce the rapidly growing epidemic of these diseases in India,” says Dr Yajnik.

For the analysis, participants were divided into four groups. At 28 weeks of pregnancy, 44 women fell into the highest quartile of fasting blood glucose, while 38 were in the highest quartile for the area under the glucose curve during glucose tolerance testing (this shows how high the blood glucose rose during the test). These women showed higher blood glucose levels from childhood and puberty through pregnancy and after delivery. They also had higher pre-pregnancy HbA1c levels, reflecting long-term elevated blood sugar.

High childhood glucose levels increased the odds of high glucose during pregnancy two-fold and post-delivery five-fold. “Our results show that higher pregnancy glycaemia reflects persistently higher glycaemia since childhood,” says Dr Yajnik.

The study argues that the most critical window for intergenerational programming of diabetes lies before and around conception. This period is missed in current clinical practice, where gestational diabetes is diagnosed only after pregnancy is established. Even screening before 20 weeks may be too late. Tracking metabolism and prioritising girls’ health much earlier is essential.

The researchers also call for closer consideration of a mother’s genetic background, socio-economic conditions, pre-pregnancy weight and metabolic status to improve outcomes in offspring. “Gestational diabetes,” argues Dr Yajnik, “is not a one-size-fits-all condition, nor one confined to pregnancy alone. Indian babies are among the smallest globally, yet current diagnostic and management guidelines for gestational diabetes are largely based on Western data. Indian health authorities must design national studies tailored to local realities and develop customised strategies to address metabolic health challenges.”