Higher BMI Linked to Pregnancy Risks in Type 2 Diabetes, Australian Study Says
Higher pre-pregnancy body mass index may increase the risk of pre-eclampsia and preterm delivery among women managing type 2 diabetes, according to an Australian retrospective cohort study published on October 1, 2026, in the Journal of Diabetes Investigation by Zhen and colleagues.
- Each 1 kg/m² increase in BMI above the normal range raises the adjusted odds of pre-eclampsia by 8.2% in women with type 2 diabetes.
- Preterm delivery risk increases by 4.2% for every additional 1 kg/m² of BMI among patients with type 2 diabetes.
- While type 1 diabetes pregnancies showed no direct statistical link between rising BMI and pre-eclampsia or preterm delivery, higher BMI strongly correlated with poorer first-trimester glycemic control and excessive gestational weight gain.
Sydney Hospital Study Compares Diabetes Types in Pregnancy
The retrospective analysis evaluated 264 singleton pregnancies managed between 2010 and 2019 at a quaternary hospital in metropolitan Sydney, Australia. Investigators separated the cohort into two distinct clinical groups: 124 pregnancies affected by type 1 diabetes and 140 pregnancies affected by type 2 diabetes. Baseline anthropometric data revealed marked differences in adiposity between the cohorts. Among women with type 1 diabetes, 46% presented with overweight or obesity. In stark contrast, 90% of women with type 2 diabetes fell into the overweight or obese categories.
Pre-Eclampsia and Preterm Delivery Risks in Type 2 Diabetes
Adverse maternal outcomes scaled sharply with rising body mass index specifically within the type 2 diabetes population. Pre-eclampsia developed in 20.5% of women with obesity, compared to 2.7% of those with overweight and 7.7% of women with normal weight. Adjusting for potential confounders, researchers calculated that every 1 kg/m² increase in BMI above the ethnicity-adjusted upper limit of normal yielded an adjusted odds ratio of 1.082 for pre-eclampsia. A parallel escalation appeared in preterm delivery rates, which reached 42.2% in women with type 2 diabetes and obesity, alongside 30.6% for those with overweight. None of the evaluable normal-weight women with type 2 diabetes experienced a preterm delivery, and each additional 1 kg/m² of BMI drove a 4.2% increase in adjusted odds for early delivery.
Glycemic Control and Complications in Type 1 Diabetes
Conversely, the study identified divergent risk patterns among pregnancies complicated by type 1 diabetes, where rising BMI showed no independent association with pre-eclampsia, preterm delivery, or infants born large for gestational age. Instead, excess weight directly hampered glycemic management during early gestation. First-trimester glycated hemoglobin (HbA1c) exceeded the 6.5% clinical threshold in 45.5% of normal-weight women with type 1 diabetes, compared with 73.2% of those with overweight and 78.6% of those with obesity. Relative to normal-weight peers, overweight carried nearly three times the adjusted odds of missing this early glycemic target, while obesity carried approximately fourfold higher odds.
The Australian findings arrive alongside separate epidemiological data presented at the European Association for the Study of Diabetes annual meeting in Milan by Maria Houborg Petersen and colleagues from the Steno Diabetes Center Odense, who examined data from the Danish Centre for Strategic Research in Type 2 Diabetes. That analysis revealed that women with a history of gestational diabetes developed type 2 diabetes at a median age of 43.5 years, compared to 56.3 years for women without such history. Approximately 40% of women with prior gestational diabetes received a type 2 diabetes diagnosis before age 40, and a higher percentage required insulin therapy shortly after onset. Petersen noted that these patients appear to develop a distinct phenotype characterized by potentially greater severity, which means intensive postpartum screening and specialized endocrinological oversight are necessary.
Disclaimer: The information provided in this article is for educational and scientific communication purposes only and does not constitute medical advice. Always consult with a qualified healthcare provider regarding any medical condition, diagnosis, or treatment plan.