Gestational diabetes explained: causes, care and safe pregnancy

What gestational diabetes is

Gestational diabetes is diabetes that first appears during pregnancy, usually in the second or third trimester. During pregnancy, the body naturally becomes more resistant to insulin — the hormone that controls blood sugar — so that more glucose is available for the growing baby. In some women the body cannot make enough extra insulin to keep up, and blood sugar levels rise too high. This is gestational diabetes. It is different from type 1 or type 2 diabetes, and in most women it disappears soon after birth. However, it is an important signal that the body finds it harder to manage blood sugar, which matters for the future as well as the pregnancy.

Who is more at risk

Some women are more likely to develop gestational diabetes than others. Risk is higher if you have a raised body weight, have had gestational diabetes before, have previously had a large baby, have a parent or sibling with diabetes, or are of South Asian, Black, African-Caribbean or Middle Eastern family background. Age and certain pregnancy findings can also raise the risk. Because of this, UK maternity care offers testing to women with these risk factors rather than testing everyone. Having a risk factor does not mean you will definitely develop the condition — it simply means screening is recommended so that, if it does occur, it can be found and managed early.

How it is diagnosed

Gestational diabetes usually causes no obvious symptoms, which is why testing matters. In the UK, women with risk factors are offered a test called an oral glucose tolerance test, usually around the middle of pregnancy. For this test you fast beforehand, have a blood sample taken, drink a sugary glucose drink, and have blood taken again a couple of hours later to see how your body handles the sugar. If your levels are above the agreed thresholds, gestational diabetes is diagnosed. Women who have had it before may be offered testing earlier or self-monitoring. Occasionally sugar found in the urine at a routine check prompts further testing too.

How it is managed

The foundation of managing gestational diabetes is a healthy, balanced diet and regular gentle activity, which help keep blood sugar steady. Women are usually taught to check their own blood sugar at home with a finger-prick test at set times, so levels can be tracked. If diet and activity are not enough to reach target levels, medicine is added — often tablets, and sometimes insulin injections, both of which are safe in pregnancy. The pregnancy is monitored more closely, with extra scans to check the baby's growth and wellbeing, because gestational diabetes can make babies grow larger. A team of midwives, doctors and diabetes specialists shares this care.

Birth, afterwards and the future

With good control, most women with gestational diabetes have a healthy baby. The timing and method of birth are planned individually, and the baby's blood sugar is checked in the hours after birth because it can dip low at first. Most women's blood sugar returns to normal soon after the placenta is delivered, and any diabetes medicine started in pregnancy is usually stopped. A follow-up blood test is arranged a few weeks later to confirm levels have settled. Importantly, having gestational diabetes raises the future risk of type 2 diabetes, so a yearly blood test and a healthy lifestyle are recommended long-term, along with earlier testing in any future pregnancy.