Spain Study: Most Pregnant Women with Type 1 Diabetes Miss CGM Glucose Targets — But Technology Helps

A study from Spain, conducted by researchers at the Institut de Recerca de l'Hospital de la Santa Creu i Sant Pau in Barcelona, reveals that the vast majority of pregnant women with Type 1 diabetes are not meeting recommended continuous glucose monitoring (CGM) targets — but using real-time CGM technology dramatically improves their chances of doing so, and leads to better outcomes for both mother and newborn.

What the Researchers Did

The Spanish team analyzed data from the landmark international CONCEPTT trial, which compared real-time CGM to traditional fingerstick blood sugar testing in pregnant women with Type 1 diabetes. They tracked glucose control across all three trimesters in over 200 participants, measuring how often women achieved three key CGM benchmarks:

• Time-in-Range (TIR): More than 70% of readings between 63–140 mg/dL (3.5–7.8 mmol/L)
• Time-Above-Range (TAR): Less than 25% of readings above 140 mg/dL (7.8 mmol/L)
• Time-Below-Range (TBR): Less than 4% of readings below 63 mg/dL (3.5 mmol/L)

They also tracked HbA1c targets from two major guidelines: the UK's NICE guideline (HbA1c under 6.5%) and the American Diabetes Association (ADA) target (HbA1c under 6.0% in the second and third trimesters).

What They Found

The results were sobering. In the first trimester, only 7.7% of women achieved the Time-in-Range target. That number improved to 10.2% in the second trimester and rose more meaningfully to 35.5% by the third trimester. Achieving the below-range target (avoiding too many lows) was actually the easiest benchmark — about half of women met it by the second and third trimesters.

Meeting the ADA's strict HbA1c target of under 6.0% remained difficult throughout pregnancy, with only roughly 23–28% of women achieving it at any trimester. However, women using real-time CGM were significantly more likely to hit all targets by 34 weeks gestation.

Critically, achieving the ADA HbA1c target was linked to a lower risk of preterm birth, large-for-gestational-age babies, and newborn low blood sugar. Interestingly, consistently staying out of the low range (TBR target) was unexpectedly associated with a higher risk of pre-eclampsia and neonatal hypoglycemia — a finding the authors say needs further investigation.

Why This Matters for US Patients

For American women with Type 1 diabetes who are pregnant or planning pregnancy, this Spanish research carries a direct and urgent message: the ADA's own targets are difficult to reach, but they matter enormously. Hitting that under-6.0% HbA1c goal in pregnancy is associated with real, measurable reductions in serious complications.

The good news is that real-time CGM — devices like the Dexcom G7 or Libre 3, which are widely available in the US — was the single biggest factor in helping women reach these targets. If you are a woman with Type 1 diabetes considering pregnancy, or currently pregnant, talk to your endocrinologist about optimizing CGM use now. US guidelines already recommend CGM in this population, and this international data strongly reinforces why.

The unexpected finding around Time-Below-Range and increased risk is a reminder that avoiding lows alone is not a complete strategy — overall glucose balance matters, and your care team should be helping you optimize the full picture.

Study Reference

Tundidor, Meek, & Yamamoto. "Continuous Glucose Monitoring Time-in-Range and HbA1c Targets in Pregnant Women with Type 1 Diabetes." Diabetes Technology & Therapeutics, 2021. PMID: 33945304. DOI: 10.1089/dia.2021.0073