Type 1 Diabetes in Pregnancy

This is a different guideline from gestational diabetes

Pre-existing type 1 diabetes and gestational diabetes are covered by the same NICE guideline, NG3, but by different recommendations with different numbers. If you have searched for blood sugar targets and found a page about a glucose tolerance test, that page was not about you. You will not be offered an OGTT, because you already have a diagnosis.

The HbA1c numbers, and what they are for

NICE (UK), NG3 recommendation 1.1.18: advise women with diabetes who are planning a pregnancy "to aim to keep their HbA1c level below 48 mmol/mol (6.5%), if this is achievable without causing problematic hypoglycaemia".

NICE NG3 recommendation 1.1.20: "strongly advise women with diabetes whose HbA1c level is above 86 mmol/mol (10%) not to get pregnant until their HbA1c level is lower, because of the associated risks."

Once pregnant, recommendation 1.3.7 says to measure HbA1c at the booking appointment for everyone with pre-existing diabetes, "to determine the level of risk for the pregnancy", and 1.3.9 says risk increases above 48 mmol/mol (6.5%). Importantly, recommendation 1.3.11 says do not routinely use HbA1c to assess control in the second and third trimesters. HbA1c is a risk marker at booking, not your day-to-day scorecard.

Recommendation 1.1.19 is the one worth holding onto if your number is higher than you wanted: any reduction towards the target "is likely to reduce the risk of congenital malformations in the baby". This is not pass or fail.

The daily targets

NG3 recommendation 1.3.5 asks for capillary plasma glucose below 5.3 mmol/litre fasting, and either below 7.8 mmol/litre one hour after meals or below 6.4 mmol/litre two hours after meals, "if these are achievable without causing problematic hypoglycaemia". Recommendation 1.3.6 adds a floor for anyone on insulin: stay above 4 mmol/litre.

Recommendation 1.3.16 offers real-time continuous glucose monitoring to all pregnant women with type 1 diabetes, "to help them meet their pregnancy blood glucose targets and improve neonatal outcomes", with intermittently scanned monitoring, commonly called flash, offered to those who cannot use real-time monitoring or who prefer it. If you have type 1 and no sensor, that is a conversation to have at your first joint clinic appointment.

NG3 also asks for blood ketone testing strips and a meter for pregnant women with type 1, with advice to test if you become hyperglycaemic or unwell, and says suspected diabetic ketoacidosis means immediate admission for level 2 critical care. DKA in pregnancy can happen at lower glucose levels than you may be used to, which is why the ketone strips matter.

The extra checks nobody warns you about

Two organ systems get specific attention, because pregnancy can accelerate existing damage.

Eyes. NG3 recommendation 1.3.25 says that after your first antenatal appointment you should be offered a retinal assessment by digital imaging with mydriasis unless you have had one in the last 3 months; if you have diabetic retinopathy, an additional assessment at 16 to 20 weeks; and another at 28 weeks for everyone. Recommendation 1.1.31 adds a preconception detail that catches people out: defer rapid tightening of glucose control until after retinal assessment and any treatment.

Kidneys. A renal assessment is offered if you have not had one in the previous 3 months.

Your baby is watched too. NG3 asks for a 20-week scan that specifically examines the fetal heart (four chambers, outflow tracts and three vessels), then ultrasound monitoring of growth and amniotic fluid volume every 4 weeks from 28 to 36 weeks. Routine fetal wellbeing testing before 38 weeks, such as umbilical artery Doppler or biophysical profile, is not recommended unless there is a specific risk of growth restriction.

When your baby will be born

NICE NG3 recommendation 1.4.2: advise pregnant women with type 1 or type 2 diabetes and no other complications to have an elective birth by induced labour, or caesarean if indicated, "between 37 weeks and 38 weeks plus 6 days of pregnancy". Recommendation 1.4.3 says consider birth before 37 weeks if there are metabolic or other complications.

Compare that with the gestational diabetes window in the same guideline, recommendation 1.4.4: no later than 40 weeks plus 6 days. Those are different numbers for different conditions, and confusing them is one of the most common errors in online summaries.

NG3 recommendation 1.4.6 also states plainly that diabetes is not a contraindication to vaginal birth after a previous caesarean.

In labour, and straight afterwards

NG3 recommendation 1.4.10 asks for capillary plasma glucose to be monitored every hour during labour and birth and kept between 4 and 7 mmol/litre. Recommendation 1.4.11 says to consider an intravenous dextrose and insulin infusion from the onset of established labour for women with type 1 diabetes. NG3 also asks for an anaesthetic assessment in the third trimester if you have comorbidities such as obesity or autonomic neuropathy.

Your insulin requirement drops sharply after the placenta is delivered, so expect your regimen to be reviewed immediately rather than in a week. Babies are watched for low blood glucose, and early feeding is part of preventing it.

Where the guidance differs

ACOG's Practice Bulletin No. 201 on pregestational diabetes describes it as "one of the most challenging medical complications of pregnancy" and notes that, because few well-designed studies exist, "many of the guidelines are based on expert and consensus opinion". That candour is useful: the numbers above are UK consensus positions built on limited trial evidence, not laws of nature. Diabetes UK and HSE Ireland describe the same broad pathway of joint clinic care, tighter targets and earlier planned birth for people using their respective health services.