High Blood Sugar in Pregnancy Raises Preterm Birth Risk

What Was Studied and Why It Matters

Preterm birth — being born before 37 weeks — is one of the leading causes of infant health problems and death worldwide. Researchers in China wanted to understand whether a mother's blood sugar levels during pregnancy, even at levels below the threshold for a formal gestational diabetes (GDM) diagnosis, could raise the risk of delivering early.

The study followed 6,842 pregnant women at a major hospital between 2016 and 2022, making it one of the larger real-world studies on this topic.

How the Study Worked

Between 24 and 28 weeks of pregnancy, each woman completed a standard oral glucose tolerance test (OGTT). This involves drinking a sugary solution and having blood drawn at three points: before drinking (fasting), one hour after, and two hours after. Researchers then tracked which women delivered prematurely.

About 7.9% of the women were diagnosed with gestational diabetes, and 5.9% had a preterm birth.

What the Researchers Found

The key finding was clear and consistent: the higher a woman's blood sugar at any of the three test points, the greater her risk of preterm birth. This relationship was steady and linear — meaning risk increased gradually with blood sugar, not just after crossing a diagnostic cutoff.

• Fasting glucose: Each unit increase raised preterm birth risk by 26%
• One-hour glucose: Each unit increase raised risk by 10%
• Two-hour glucose: Each unit increase raised risk by 10%

Importantly, these associations held up even after accounting for other factors that could influence outcomes.

What This Means for Real Patients

This research sends a practical message: blood sugar management during pregnancy matters — and it matters across the entire range of glucose levels, not just for women who receive a GDM diagnosis.

If you are pregnant or planning to become pregnant, talk to your care team about glucose monitoring. Women managing blood sugar during pregnancy rely on accurate, reliable tools — from glucose meters to test strips — and having dependable supplies on hand makes consistent monitoring much easier. MDS Diabetes offers a wide range of diabetes management supplies that can support pregnant women in staying on top of their daily readings.

Diet, physical activity, stress management, and in some cases medication, can all help keep blood sugar within a healthy range. The good news highlighted by this study: unlike many pregnancy risks, elevated blood sugar is something that can be addressed with the right support.

Bottom Line

Even modest rises in blood sugar during the second trimester of pregnancy are linked to a meaningfully higher risk of preterm birth. This study reinforces why glucose screening between 24–28 weeks is so important — and why acting on the results, not just recording them, can make a real difference for mother and baby.