Never before have so many pregnant women developed gestational diabetes

Recent figures from the Norwegian Institute of Public Health (NIPH) reveal that record numbers of pregnant women are being treated for gestational diabetes.

For many, it may seem like a temporary problem that disappears after giving birth.

But gestational diabetes also increases the risk of type 2 diabetes later in life, for both mother and child.

“Our aim has been to find out how similar or different gestational diabetes and type 2 diabetes really are,” says Gunn-Helen Moen.

She is a researcher at the University of Oslo's Institute of Clinical Medicine.

“What are the underlying reasons why some women develop gestational diabetes? And why do some go on to develop type 2 diabetes so soon after pregnancy?” she asks.

The researchers have brought new insight into why some women are particularly prone to gestational diabetes.

"Our genes appear to play a far greater role than previously assumed," says Moen.

Gestational diabetes has its own genetic signature

A genetic variant is a small difference in our genetic material (DNA) that can affect how the body functions. For example, how susceptible we are to developing a disease.

Moen and her colleagues have identified 37 genetic variants that are associated with gestational diabetes.

They then examined how strongly these variants are linked to type 2 diabetes.

They found that 12 of these genetic variants appear to be more strongly associated with pregnancy and gestational diabetes than with type 2 diabetes.

“There are several genetic variants that may help determine who develops gestational diabetes,” says Moen. “This suggests that the condition is not merely an early warning sign of type 2 diabetes. Gestational diabetes also has its own genetic causes and characteristics.”

What is gestational diabetes?

Pregnancy triggers major changes in the body’s metabolism, designed  to ensure that the foetus receives enough energy throughout the entire pregnancy, Moen explains.

“During pregnancy, insulin resistance increases, the body produces more insulin, and blood sugar levels fluctuate more than usual,” she says.

Insulin resistance is a condition in which the body’s cells become less sensitive to the hormone insulin. Because insulin works less effectively, the pancreas has to produce more insulin to keep blood sugar levels normal.

“Gestational diabetes occurs when these adaptations do not work as they should. In some women, this happens because the body becomes too insulin resistant, meaning that the body does not use insulin as effectively as it ought to. In others, it is because the body cannot produce enough insulin,” the researcher says.

The result is high blood sugar levels in the mother. The foetus then has to produce more insulin itself, which can lead to excessive growth in the womb.

“Gestational diabetes can cause complications for both mother and baby, so it's a condition that requires careful monitoring,” says Moen.

The condition increases the risk of a difficult birth, caesarean section, premature birth, stillbirth, and low blood sugar in the newborn baby.

Genes reveal who is most at risk

The genetic variants identified by the researchers provide clues as to who is most vulnerable to developing gestational diabetes.

The findings suggest that some women are predisposed to the condition even before they become pregnant, and that pregnancy then acts as a trigger.

This supports the view that gestational diabetes is, at least in part, a distinct condition in its own right, and offers a deeper understanding of what causes it.

“In the longer term, this knowledge may help us to better identify women at high risk of developing gestational diabetes during pregnancy, and to determine who should be followed up more closely after giving birth,” says Moen.

At the same time, there is considerable overlap, as several of the genetic variants also increase the risk of developing type 2 diabetes later in life.

“The findings may also help us understand why some women progress very quickly to type 2 diabetes after a pregnancy,” says Moen.

The world’s largest genetic study of gestational diabetes

The researchers analysed genetic data from almost one million women. They examined and compared genetic variants from around 38,000 women with gestational diabetes and over 700,000 women without the condition.

The data came from more than 30 selected groups in Europe, the USA, and Asia.

“Several previous studies of gestational diabetes have included only one ethnic group. When a study is limited to a single population, we still know relatively little about how the picture looks in other parts of the world,” says Moen.

In the new study, the researchers included participants with diverse backgrounds.

"This is the largest analysis to date of gestational diabetes across different populations and across generations,” she says.

This is important because the prevalence of the condition varies greatly between countries. These differences are linked to factors such as ethnic background, levels of overweight and obesity, and how doctors screen for and diagnose the condition.

More research is needed

The researchers also investigated whether the effect of genetic variants on blood sugar regulation in pregnancy differs between population groups.

Moen emphasises that more research is needed before these findings can be translated into concrete changes in clinical practice.

“This study helps us identify which genes may play a role. It's an important step towards a better understanding and better follow-up of women who are affected. However, we still need further research before we can provide specific, evidence-based advice to pregnant women and to healthcare professionals,” she says.

Reference:

Nunes et al. Multi-ancestry, trans-generational GWAS meta-analysis of gestational diabetes and glycaemic traits during pregnancy reveals limited evidence of pregnancy-specific genetic effects, Nature Communications, 2026. DOI: 10.1038/s41467-026-73509-y

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Read the Norwegian version of this article on forskning.no

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