Dutch Study: How CGM Readings During Pregnancy Predict Baby Size in Insulin-Treated Diabetes

A study from the Netherlands offers important new insight into how continuous glucose monitoring (CGM) readings during pregnancy can predict the risk of having a larger-than-normal baby — a complication that can make delivery dangerous for both mother and child. Conducted at Amsterdam UMC, one of Europe's leading academic medical centers, this research analyzed data from the GlucoMOMS randomized controlled trial and is particularly relevant for American women managing insulin-treated diabetes during pregnancy.

Why an International Perspective Matters

The Netherlands has long been a leader in obstetric care and diabetes management. European researchers often use slightly different glucose target ranges and CGM monitoring protocols than US clinicians, making their findings a valuable lens for comparing and refining American practice. This study's large, well-controlled dataset helps fill gaps in understanding which CGM measurements matter most — and when — during each trimester of pregnancy.

What the Study Found

Researchers studied 115 pregnant women with insulin-treated diabetes — 50 with Type 1 diabetes and 65 with Type 2 diabetes or insulin-treated gestational diabetes mellitus (GDM). They tracked CGM metrics across each trimester and looked for links to five key outcomes: neonatal hypoglycemia, pre-eclampsia, preterm birth, large for gestational age (LGA) babies, and NICU admissions.

The glucose target range used was 63–140 mg/dL (3.5–7.8 mmol/L) — slightly broader than the American Diabetes Association's recommended pregnancy target of 63–140 mg/dL, which aligns closely with this Dutch protocol.

Key findings broke down by diabetes type:

• Type 1 Diabetes: A higher average (mean) glucose during the second trimester was significantly associated with delivering an LGA baby, with an odds ratio of 2.6. In practical terms, elevated average glucose readings — not just occasional spikes — appear to be the primary driver of excessive fetal growth.
• Type 2 Diabetes / Insulin-Treated GDM: The key risk factor was the "area under the curve above limit" — essentially, the total accumulated time and degree that glucose exceeded 140 mg/dL. Women with higher values in this metric were dramatically more likely (odds ratio: 10.0) to deliver an LGA baby.

Importantly, no CGM metric was significantly associated with neonatal hypoglycemia, pre-eclampsia, preterm birth, shoulder dystocia, or NICU admissions across any diabetes type.

Why This Matters for US Patients

In the United States, CGM use during pregnancy is growing rapidly, but clinical guidance on which CGM metrics to prioritize is still evolving. This Dutch study suggests that American clinicians and patients should focus on different numbers depending on diabetes type. For women with Type 1 diabetes, keeping the overall average glucose low throughout the second trimester is critical. For women with Type 2 diabetes or GDM on insulin, minimizing time and degree spent above 140 mg/dL may be the most important goal to prevent an overly large baby — which raises risks for C-section, birth injury, and shoulder dystocia during delivery.

US patients using CGM devices like the Dexcom G7 or Freestyle Libre should ask their OB or endocrinologist to review not just their time-in-range, but these specific metrics, particularly during the second trimester.

Study Citation

Rademaker, van der Wel, van Eekelen. "Continuous glucose monitoring metrics and pregnancy outcomes in insulin-treated diabetes: A post-hoc analysis of the GlucoMOMS trial." Diabetes, Obesity & Metabolism, 2023. PMID: 37735847. DOI: 10.1111/dom.15276