Recent figures from the Norwegian Institute of Public Health (FHI) 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 birth. However, 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, a researcher at the Institute of Clinical Medicine at the University of Oslo.
"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?"
The team's work has 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.
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 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. Of the 37, 12 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."
The study has been published in the prestigious journal Nature Communications.
What is gestational diabetes?
Pregnancy triggers major changes in the body's metabolism, designed to ensure that the foetus receives enough energy throughout the gestational period.
"During pregnancy, insulin resistance increases, the body produces more insulin, and blood sugar levels fluctuate more than usual," explains Moen.
"Gestational diabetes occurs when these adaptations do not work as they should. In some women, this happens because the body becomes too insulin resistant - it does not use insulin as effectively as it ought to. In others, it is because the body cannot produce enough insulin."
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 is 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, because 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," she adds.
The world's largest genetic study of gestational diabetes
To explore these questions, 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 cohorts in Europe, the USA and Asia.
"Several previous studies of gestational diabetes have included only one ethnic group," Moen explains. "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."
"In our study, we included participants with diverse backgrounds. This is the largest analysis to date of gestational diabetes across different populations and across generations."
This is important because the prevalence of gestational diabetes varies significantly between countries. These differences are linked to factors such as ethnic background, levels of overweight and obesity, and how the condition is screened for and diagnosed.
The researchers also investigated whether the effect of genetic variants on blood sugar regulation in pregnancy differs between population groups.
More research needed before clinical change
Moen emphasises that more research is required before these findings can be translated into concrete changes in clinical practice.
"This study helps us identify which genes may play a role. It is an important step towards better understanding and better follow-up of women who are affected," she says.
"However, we still need further research before we can provide specific, evidence-based advice to pregnant women and to healthcare professionals."
Reference
Brito Nunes, C., Rukins, V., Cisse, A.H. 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. Nat Commun 17, 4726 (2026). https://doi.org/10.1038/s41467-026-73509-y
