What is the issue?

Diabetes mellitus can be caused by autoimmune destruction of the cells producing insulin, so that levels are reduced (type 1 diabetes), or the body tissues becoming resistant to insulin (type 2 diabetes). The end result is increased blood glucose levels. Insulin is used to regulate glucose levels for pregnant women with type 1 diabetes. For women with type 2 diabetes, lifestyle changes, including diet and exercise, are an important part of treatment. An oral anti-diabetic drug (medication that aims to reduce blood sugar levels) or insulin may be added to lower blood glucose levels. We set out to evaluate the effects of exercise interventions, for pregnant women with pre-existing type 1 or 2 diabetes, on birth outcomes for the mother and her baby. An earlier review on the effects of exercise on diabetes during pregnancy has been split into two reviews – one for women with gestational diabetes, and this review, on women with pre-existing diabetes.

Why is this important?

Women with diabetes, who become pregnant, are at increased risk of pregnancy loss, or having a baby that is large-for-gestational age (baby is larger than would be expected for the number of weeks of pregnancy), is born preterm, who dies around the time of birth, or is born with birth defects. The newborn baby may also have blood sugar levels that are lower than normal, low calcium levels, and excess bilirubin in the blood. Long-term follow-up of the infants of diabetic mothers suggests that they are at increased risk of obesity and type 2 diabetes when older.

The number of women who already have diabetes when they become pregnant is increasing, and identifying ways to improve health outcomes for women with diabetes and their babies is a priority. We already know that exercise may be of benefit for non-pregnant women with type 2 diabetes, as it improves their blood glucose levels and reduces triglyceride fats in the blood. We are unclear if exercise benefits, and is safe for, pregnant women with pre-existing diabetes and their babies. Physical activity could help to increase fitness and prevent stress urinary incontinence, lower back pain, or depression, and control weight gain during pregnancy.

What evidence did we find?

We searched for evidence on 27 June 2017. We did not identify any randomised controlled trials (RCT) that compared any type of exercise programme (plus standard care) for pregnant women with pre-existing diabetes with 1) standard care alone, or 2) standard care plus another exercise programme.

What does this mean?

There is no evidence from RCTs to evaluate the effects of exercise interventions for improving mother and baby outcomes in women with pre-existing diabetes.

Good quality, large studies are urgently needed to find out if exercise interventions are safe, and if they improve health outcomes for pregnant women with diabetes and their babies. Future studies in this area could utilise the outcomes listed in this review, to improve consistency between trials in this area, and aid future analyses.