Episode 31 — Pregnancy with Type 1 Diabetes: The Evidence-Based Roadmap

In this episode

Pregnancy with type 1 diabetes requires navigating intense physiological changes, shifting insulin needs, tight glucose targets, and an overwhelming amount of clinical information — often delivered at the worst possible time. Professor Eleanor Scott, one of the UK’s leading experts in pregnancy and diabetes, breaks down what actually matters: the glucose targets that protect both mother and baby, which technologies have robust evidence, how to handle the dramatic insulin swings across trimesters, and why planning makes such a difference.

The pregnancy roadmap

• Pre-pregnancy: Optimise glucose (HbA1c below 48 mmol/mol / 6.5%), start 5 mg folic acid, check vitamin D, aim for 70% time in pregnancy range (3.5–7.8 mmol/L or 63–140 mg/dL) ideally for at least one month before conception.
• First trimester (weeks 1–12): Increased insulin sensitivity, frequent lows, nausea complicates bolusing — high variability is normal physiology during this phase.
• Second and third trimesters (weeks 13–40): Insulin resistance climbs dramatically — insulin-to-carb ratios can increase three to five times baseline, requiring progressive weekly adjustments.
• Delivery and postpartum: Insulin needs drop immediately back to pre-pregnancy levels once the placenta is delivered; breastfeeding may require further reductions.
• Technology first-line: Pregnancy-specific hybrid closed-loop systems (CamAPS FX) and CGM are now standard care in the UK — they reduce burden, improve outcomes, and save NHS resources.

Key themes

1. Glucose targets are tight in pregnancy — and for good reason

The pregnancy glucose target range is 3.5–7.8 mmol/L (63–140 mg/dL), with a goal of 70% time in range. This is tighter than the standard type 1 diabetes range (3.9–10.0 mmol/L) because babies are sensitive to raised glucose — high levels increase risk of miscarriage, congenital malformations, preterm delivery, large babies, and neonatal intensive care admissions.

2. Planning matters — but unplanned pregnancy is not catastrophic

Ideally, glucose control should be optimised before conception. High HbA1c at conception increases risks, but the absolute risk of complications is still around 10% — not inevitable. If pregnancy is unplanned, contact your diabetes team immediately. Every improvement in glucose from that point forward reduces risk. Early intervention still makes a substantial difference.

3. First trimester: insulin sensitivity and variability

The first twelve weeks bring increased insulin sensitivity, frequent hypoglycaemia, nausea, vomiting, and highly variable glucose levels. Many women struggle despite doing everything right — this is normal physiology, not failure. Pregnancy-specific hybrid closed-loop systems handle this variability far better than manual adjustments.

4. Second and third trimesters: marked insulin resistance

Insulin needs climb dramatically — insulin-to-carb ratios can increase from 1:10 to 1:3 or even 1:2. This is expected physiology driven by placental hormones, not a sign of poor control. Basal rates and bolus doses need progressive weekly adjustments. Pre-bolusing becomes particularly important (15–20 minutes with hybrid closed-loop).

5. CGM is standard care in pregnancy

The CONCEPTT trial showed that CGM in pregnancy improves time in range, reduces large-for-gestational-age babies, lowers preterm delivery rates, and cuts neonatal intensive care admissions. Real-world NHS data confirms these benefits — and CGM saves NHS resources compared with fingerprick testing alone. CGM is now standard care for pregnancy with type 1 diabetes in the UK.

6. Pregnancy-specific hybrid closed-loop systems have the strongest evidence

Not all hybrid closed-loop systems are equal in pregnancy. CamAPS FX is the only one with robust randomised controlled trial evidence (AiDAPT trial) showing improved time in range, reduced gestational weight gain, lower rates of large-for-gestational-age babies, reduced neonatal hypoglycaemia, and less maternal burden. It was developed specifically for pregnancy with an adaptive algorithm that prioritises recent glucose data over historical patterns — essential in pregnancy’s rapidly changing physiology.

NHS England has created a switching fund allowing women to temporarily switch to CamAPS FX for pregnancy, even if they use a different system outside pregnancy.

7. MDI may outperform standard pumps in pregnancy

Audit data suggests that multiple daily injections may achieve better outcomes than standard pump therapy (non-hybrid closed-loop) in pregnancy. However, pregnancy-specific hybrid closed-loop systems vastly outperform both MDI and standard pumps where available.

8. Delivery: insulin needs drop immediately

Once the baby and placenta are delivered, insulin needs return to pre-pregnancy levels. A safe starting point is reducing basal insulin by around 50% and returning carb ratios to pre-pregnancy levels (or slightly lower if breastfeeding). Hypoglycaemia is common postpartum if insulin is not reduced promptly — this requires proactive planning.

9. Breastfeeding lowers insulin needs further

Breastfeeding uses significant energy, further reducing insulin requirements. Carb ratios may need adjustment, and having snacks readily available during feeds helps prevent lows. Milk supply can take a few days to establish, so insulin needs may shift again once breastfeeding is fully established.

10. Lifestyle tactics that tend to help

• Pre-bolus: 15–20 minutes before meals (even on hybrid closed-loop) — this tends to matter more than almost anything else for post-meal glucose.
• Mixed meals: Combine protein, fat, and vegetables with carbohydrate to slow absorption and match insulin action.
• Moderate carbohydrate intake: Aim for 30–40% of total intake — large carb loads are harder to match with insulin in pregnancy.
• Walking after meals: 10–15 minutes of light movement post-meal tends to smooth glucose peaks.
• Routine and predictability: Eating similar amounts at similar times helps both hybrid closed-loop algorithms and manual management adapt to changing insulin needs.

11. Ketone awareness: act earlier in pregnancy

Diabetic ketoacidosis can develop faster in pregnancy. If glucose is persistently high (above 14 mmol/L for 90 minutes) despite insulin corrections, check for pump and cannula issues and check ketones. Seek medical advice if ketones are 1.5 mmol/L or above — the threshold is much lower in pregnancy than outside it.

12. One high glucose is not catastrophic

What matters is time in range averaged over days and weeks, not perfection every hour. Reframe CGM as information: “What happened? What’s the likely driver? What’s one tweak for next time?” This reduces anxiety and avoids the paralysis that comes from fear of imperfection.

Practical exploration checklist

Before pregnancy (or as soon as possible)

• Contact your diabetes team to discuss pregnancy planning
• Start 5 mg folic acid daily (requires prescription)
• Check vitamin D levels and supplement if needed
• Aim for HbA1c below 48 mmol/mol (6.5%) and 70% time in pregnancy range (3.5–7.8 mmol/L)
• If not already using CGM, get set up with continuous glucose monitoring
• Discuss switching to a pregnancy-specific hybrid closed-loop system (CamAPS FX is first-line in the UK)

First trimester (weeks 1–12)

• Contact your diabetes team as soon as you know you are pregnant
• Expect increased insulin sensitivity and hypoglycaemia — reduce basal insulin as needed
• If nauseated, bolus after meals rather than before to reduce hypoglycaemia risk from vomiting
• Eat small, frequent mixed meals
• Accept that glucose will be variable — this is normal physiology, not failure

Second and third trimesters (weeks 13–40)

• Expect insulin needs to climb progressively (three to five times baseline)
• Strengthen insulin-to-carb ratios progressively — do not wait until glucose is already high
• Pre-bolus 15–20 minutes before meals
• Walk for 10–15 minutes after eating if possible
• Keep carbohydrate intake moderate (30–40% of total intake)
• Discuss ketone testing with your team if glucose is persistently high

Delivery and postpartum

• Reduce insulin after delivery: basal by around 50%, carb ratios back to pre-pregnancy levels
• If breastfeeding, further reductions may be needed
• Keep snacks readily available during feeds

About the guest

Professor Eleanor Scott is a consultant physician and one of the UK’s leading experts in pregnancy and maternal health in type 1 diabetes. She runs the pregnancy and diabetes service at Leeds Teaching Hospitals NHS Trust, leads a research group focused on pregnancy outcomes, and has shaped national and international policy on diabetes care in pregnancy. Professor Scott led the development and clinical trials of pregnancy-specific hybrid closed-loop technology and has published extensively on CGM, automated insulin delivery, and improving outcomes for women with type 1 diabetes.

Related episodes

• Episode 32 — Menstrual cycle and type 1 diabetes (Dr Cecilia Nobili)
• Episode 33 — Exercise for females with type 1 diabetes (Prof. Jane Yardley)
• Episode 7 — Fundamentals of The GNL
• Episode 8 — Activity snacking and time in range
• Episode 18 — Exercise without fear
• Episode 29 — Five Principles of T1D Behaviour Change
• Episodes 1–6 — AID Systems Guide
• Episodes 10–12 — CGM Series
• Episode 30 — Diabetotech: Educating on Algorithms