Baby on the cards? Cut back on sugar

It's long been acknowledged that gestational diabetes mellitus (GDM) can pose adverse risks to a child from the time it's in utero, all the way to adulthood. But a GUSTO study shows that even babies of mothers without GDM – but with mildly elevated glucose levels – are no less out of the woods.
By Mya Thway Tint

Ultrasound and pregnancy test
Baby photo created by freepik -

Expectant mothers are advised by obstetricians to keep their glucose levels in check for good reason. It’s long been known that offspring of mothers with pre-existing diabetes or diabetes during pregnancy (gestational diabetes mellitus or GDM) are at increased risk of childhood obesity, and obesity, diabetes and cardiovascular disease later in life.

However, it doesn’t mean that pregnant woman with glucose levels below the diagnostic cutoff for gestational diabetes are in the clear. In a study performed on the GUSTO cohort, it was found that even slightly elevated maternal glucose (hyperglycaemia) – below the diagnostic levels of gestational diabetes – can influence a newborn’s fat deposition (how fat is distributed in the body). Unfavourable fat distribution or neonatal adiposity appears to track into childhood, thereby increasing the risk for childhood obesity.

Interestingly, the data also suggests that girls may be more sensitive to such influences and gain more fat than boys.

Sweetness your baby doesn’t need
Diabetes develops when the body does not produce sufficient amounts of insulin (a hormone that controls one’s blood sugar level). This causes sugar to build up in the bloodstream instead of moving into the body’s cells where it's needed for energy, resulting in high blood glucose levels. Expectant mothers who are overweight and/or obese, have had gestational diabetes in previous pregnancies, or have a family history of diabetes are predisposed to diabetes during pregnancy.

The excess glucose from the blood of a diabetic mother travels through the placenta to the foetus, causing elevated blood glucose levels in the baby. When a foetus gets more energy from glucose than it needs to grow, the extra energy is stored as fat and the extra fat is deposited in different parts of the body, especially in the tummy. Hence, individuals with obesity and type 2 diabetes often present with a wider girth.

A big deal
A high blood sugar level during pregnancy can lead a baby to grow big (large-for-gestational-age or LGA) and have excessive neonatal adiposity. Being large-for-gestational-age poses health risks for both mother and baby. Mothers may face prolonged labour or caesarean delivery instead of normal delivery through the birth canal. LGA babies are also at higher risk of obesity, diabetes and cardiovascular disease later in life.

The findings from this study highlight that extra fat deposition is observed in babies of the mothers with elevated glucose levels, despite the levels being below the diagnostic cutoff for gestational diabetes and the babies being of average birth weight (~3.6kg). However, similar to babies of mothers with GDM, greater fat deposition was observed in babies of mothers with elevated glucose. Therefore, these infants may also develop the same long-term health problems in adulthood, such as type 2 diabetes and cardiovascular disease.


Intervention starts before pregnancy
The mothers with GDM in the GUSTO study were treated with lifestyle intervention (optimising diet and physical activity) and medication, which was successful in reducing big babies but not childhood obesity. This suggests that controlling glucose levels only during pregnancy may not be sufficient, and that perhaps managing glucose levels should begin from the time of preconception – or even earlier.

The evidence from our studies provides guidelines for healthy weight and glucose levels, allowing us to develop strategies to screen, monitor and optimise glucose levels for reproductive-age mothers before conception. It also helps these women to better understand the effect maternal glycaemia has on a baby’s fat deposition during development and in childhood, and reinforces the importance of engaging in a healthy lifestyle.

Dr Mya Thway Tint's research focuses on developmental influences of offspring's metabolic risk and bone health in reproductive-age women and children. She is involved in the GUSTO, S-PRESTO and NiPPeR studies.