Evidence suggests that risk of obesity, diabetes, and heart disease may be programmed while the fetus is developing during pregnancy and within the first few years of life. We now know that conditions experienced while in utero may shape our risk for diseases by altering how our genes are turned on and off. Researchers at SickKids, Mount Sinai Hospital, and the University of Toronto, have been collaborating in an effort to better understand the impact of early life exposures on the health outcomes of mothers and their babies. Dr. Hamilton at SickKids and Dr. Retnakaran at Mount Sinai Hospital have been studying a group of mothers with and without gestational diabetes (diabetes that is first recognized during pregnancy) and their babies, following these children from birth until age 5 years, and collecting information about child growth, body fat, sugar levels and levels of cholesterol in the blood.

Undiagnosed or untreated gestational diabetes increases the risk of having a large baby. Babies who are large may have more complications during delivery and may be at risk for low blood sugars and jaundice during the newborn phase. The health implications of gestational diabetes extend well beyond the time of birth, as babies born to mothers with gestational diabetes are more likely to become overweight and develop type 2 diabetes in childhood and adolescence. Also, while blood sugar levels usually return to normal in mothers after delivery, these women are more likely to have gestational diabetes during their next pregnancy and are also at greater risk for developing type 2 diabetes later in life.

Dr. Hamilton and Dr. Retnakaran have found that infants born to mothers with and without gestational diabetes actually had similar birth weights, likely due to the treatment of gestational diabetes in the third trimester. Nonetheless, babies of mothers who were more insulin resistant during pregnancy (insulin resistance is when the body no longer effectively uses insulin to control blood sugar levels, a condition related to diabetes) tend to gain more weight within the first year of life and have more body fat. These researchers also found that the children’s own insulin resistance was related to different factors depending on whether they were exposed to diabetes in the womb. For example, in children of mothers with gestational diabetes, it was the amount of weight gained in the first year of life that predicted their insulin resistance. These intriguing results suggest that very early differences appear between children of mothers with varying levels of insulin sensitivity.

Interestingly, while a diagnosis of gestational diabetes has important implications for the future health of babies, this research team has recently shown that maternal weight may have a stronger impact on infant birth weight than blood sugars. In a study that included 472 women without gestational diabetes, levels of sugar and cholesterol in the blood did not significantly impact the risk of having a larger than average baby. Rather, a women’s weight before pregnancy and the amount of weight she gained during pregnancy was the best predictor of whether she would give birth to a big baby. This highlights the importance of targeting healthy body weight in young women as a strategy for reducing the risk of having a big baby, and suggests that closer monitoring of weight gain during pregnancy may be necessary.


Retnakaran R, Ye C, Hanley AJ, Connelly PW, Sermer M, Zinman B, Hamilton JK: Effect of maternal weight, adipokines, glucose intolerance and lipids on infant birth weight among women without gestational diabetes mellitus. CMAJ 2012;184 (12):1353-1360

Borgono CA, Hamilton JK, Ye C, Hanley AJ, Connelly PW, Sermer M, Zinman B, Retnakaran R: Determinants of Insulin Resistance in Infants at Age 1 Year: Impact of gestational diabetes mellitus. Diabetes Care 2012;35 (8):1795-1797.

Kramer CK, Hamilton JK, Ye C, Hanley AJ, Connelly PW, Sermer M, Zinman B, Retnakaran R. Antepartum determinants of rapid early life weight gain in term infants born to women with and without gestational diabetes. Clin Endocrinol EPub ahead of print Feb 2014,