Borderline Gestational Diabetes: What Does a Borderline Result Mean?

Borderline gestational diabetes is an informal phrase, not a separate diagnosis. It usually means one oral glucose tolerance test (OGTT) value sat close to the cut-off your service uses, either just above it, so gestational diabetes was diagnosed, or just below it, so it was not.

Both situations are worth a clear conversation with your midwife or doctor. This guide explains how the cut-offs work and what to ask. It cannot tell you whether your own result counts as gestational diabetes; your care team makes that call.

A glucose result on its own is rarely an emergency, but some pregnancy symptoms are. The NHS lists gestational diabetes as raising the chance of pre-eclampsia. Get urgent help from your maternity unit, or your local urgent or emergency service if you cannot reach it, if you have:

• A severe headache that does not go away with simple painkillers, or vision problems such as blurring or flashing lights.
• Pain below the ribs, sudden swelling of the face, hands or feet, vomiting or feeling very unwell.
• Your baby moving less than usual or a change in the usual pattern of movements.
• Symptoms of high blood sugar, such as increased thirst, needing to pee more often or a dry mouth. The NHS notes some of these can be normal in pregnancy, but advises seeing a doctor promptly rather than waiting for your next test.

Testing is usually done between 24 and 28 weeks of pregnancy, according to NIDDK and the NHS. The NHS says people who had gestational diabetes before are tested soon after booking.

The NHS describes the 75-gram OGTT as a two-hour test. A blood sample is taken in the morning after fasting for 8 to 10 hours, you drink a glucose solution, and a second sample is taken two hours later. Some services take an extra sample at one hour. In the United States, many services first use a shorter glucose challenge test and only move to a full OGTT if that result is high.

NICE guidance for England diagnoses gestational diabetes if the fasting plasma glucose is 5.6 mmol/litre or above, or the 2-hour plasma glucose is 7.8 mmol/litre or above. Only one of these needs to be reached.

Different guideline bodies use different criteria. Healthdirect Australia describes a test with fasting, 1-hour and 2-hour samples, where gestational diabetes is diagnosed if any one of the three is higher than the laboratory range. MedlinePlus describes US approaches that may use a 100-gram, three-hour test with different cut-offs, so the same number can be read differently.

This means a value labelled borderline in one place could be classed differently elsewhere. Units also differ: mmol/L is used in the UK and Australia, while mg/dL is common in the US. Read your report alongside the criteria your own service uses, and ask your team to explain them rather than comparing your number with a chart from another country.

If your value was just over the cut-off, you have gestational diabetes by that service's criteria. NICE advises explaining that good blood glucose control during pregnancy reduces the risk of a very large baby, birth injury, induction or caesarean birth, low blood sugar in the newborn and perinatal death. The NHS also lists extra amniotic fluid and premature birth among possible effects.

If your value was just under, you do not have gestational diabetes by those criteria. Any risk factors that led to the test, such as a family history of diabetes or a previous large baby, still apply. NICE recommends that people who had gestational diabetes before have a further OGTT at 24 to 28 weeks if an earlier one was normal. Ask whether anything similar applies to you.

For people diagnosed with a fasting level below 7 mmol/litre, NICE recommends a trial of diet and exercise changes first, with referral to a dietitian. It gives walking for 30 minutes after a meal as an example of regular exercise. Medicine is added if targets are not met within one to two weeks; your team will explain any options.

You are usually taught to check your own blood glucose with a meter. Your team will give you the targets and timings to use, which differ between services. Healthdirect, for example, suggests checking at least four times a day, on waking and after main meals. Check with your midwife or doctor before starting a new activity.

Healthy eating and regular activity are reasonable for anyone after a near-threshold result, but do not cut out whole food groups or restrict eating sharply without advice from your team or a dietitian.

Gestational diabetes usually goes away after birth. The NHS advises a blood test for diabetes 6 to 13 weeks after giving birth, then yearly if that result is normal. Healthdirect notes that about 1 in 2 people with gestational diabetes later develop type 2 diabetes, usually 10 or more years later, and NIDDK says healthy weight, food choices and activity may lower that risk.

Bring your result with its date, units and the times each sample was taken.

• Which criteria and cut-offs does this service use, and which of my values was close to the line?
• Do I have gestational diabetes, or not, by those criteria?
• Should I check my blood glucose at home, and what targets and timings should I use?
• Can I see a dietitian, and what activity is safe for me?
• Will I have more scans or a repeat test later in pregnancy?
• When should I have a diabetes test after birth, and before any future pregnancy?

On SameCase, patients and verified doctors share de-identified cases. Seeing how others with a near-threshold glucose test described their results, monitoring and the questions they raised may help you prepare for your appointment. Each pregnancy and each service is different, so similar cases cannot tell you your diagnosis or outcome, and they do not replace your maternity team's advice.