- βIn pregnant women with type 1 diabetes, CGM metrics between weeks 28 and 30 showed the strongest link to high blood pressure disorders and large babies β suggesting this window is critical for tightening glucose control.
| Journal | Journal of diabetes science and technology |
| Year | 2026 |
| Authors | Fisher, Pavan, Villa-Tamayo |
| PMID | 41186140 |
| DOI | 10.1177/19322968251388119 |
What This Study Found
Researchers looked at continuous glucose monitor (CGM) data from 87 pregnant women with type 1 diabetes. They found that blood sugar patterns in the late second trimester β especially around weeks 28 to 30 β were strongly linked to serious pregnancy complications. Women whose CGM data showed more time above the target blood sugar range were more likely to develop high blood pressure problems or have a larger-than-normal baby.
Why This Matters for You
Pregnancy with type 1 diabetes comes with real risks β for both mom and baby. This study highlights that what your blood sugar looks like around weeks 28 to 30 of pregnancy may be one of the most important warning signs of problems ahead.
Three outcomes were studied:
- Hypertensive disorders of pregnancy (HDP) β like preeclampsia, which can be dangerous for both mother and baby
- Large-for-gestational-age (LGA) babies β when a baby grows too large, which can complicate delivery
- Neonatal hypoglycemia β low blood sugar in the newborn after birth
Importantly, 71% of the women in this study experienced at least one of these complications β even though their average A1C before pregnancy was a relatively well-controlled 6.5%. That tells us A1C alone doesn't capture the full picture. How blood sugar moves throughout the day β and especially how much time is spent above range β matters deeply during pregnancy.
What the CGM Data Showed
Women who developed high blood pressure disorders had higher average blood sugar and spent more time above the target range (above 140 mg/dL) compared to those who didn't. Women who had larger babies tended to have less time below range (below 63 mg/dL) during weeks 24 to 35.
The biggest differences between groups appeared at weeks 28 to 30 β a time when the body naturally becomes more resistant to insulin. This is a known challenge in pregnancy, but the study suggests it's also a key opportunity to intervene.
What This Means Practically
If you have type 1 diabetes and are pregnant β or planning to become pregnant β this research supports the value of wearing a CGM throughout your pregnancy. CGM gives you and your care team a real-time, detailed picture of your blood sugar that an A1C test simply cannot provide.
Knowing that the late second trimester is a critical window means your doctor may want to review your CGM data more closely during that time and make adjustments to your insulin doses or meal plan.
MDS Diabetes carries a range of CGM supplies and diabetes management tools to support you through every stage of pregnancy. Visit mdsdiabetes.com to explore options that work with your CGM system.
π Key Takeaway
In pregnant women with type 1 diabetes, CGM readings between weeks 28 and 30 showed the strongest link to high blood pressure disorders and large babies β suggesting this window is critical for tightening glucose control.
Important Limitations
This was a relatively small study (87 participants) at a single medical center, and it looked back at past records rather than following women forward in a controlled trial. The findings are promising but need to be confirmed in larger studies before they change standard care guidelines.
Full Citation
Fisher, Pavan, Villa-Tamayo (2026). Continuous Glucose Monitoring and Maternal and Neonatal Morbidity in Pregnant People With Type 1 Diabetes. Journal of Diabetes Science and Technology. PMID: 41186140. DOI: 10.1177/19322968251388119