Description of the condition

Description of the intervention

The American College of Sports Medicine defines physical activity as any bodily movement that is produced as a result of the contraction of skeletal muscle, and defines exercise as physical activity comprising planned, structured, and repetitive body movements, which are undertaken to improve one or more components of physical fitness (ACSM 2014).

Physical activity in non‐diabetic pregnant women has been shown to be beneficial. It has not been shown to be harmful to the fetus, and can potentially lead to long‐term health benefits for the mother. Observed benefits include cardio‐respiratory fitness, prevention of stress urinary incontinence, prevention of lumbar pain, decreased depression, and control of weight gain during pregnancy (Nascimento 2012).

In women with type 2 diabetes who were not pregnant, physical activity, combined with diet and hypoglycaemic medication, has been shown to be effective in maintaining glycaemic control (Tuomilehto 2001).

This evidence may not be generalisable to pregnant women with pre‐existing diabetes, but it does suggest that mild exercise during pregnancy may have the potential to reduce the risk of complications associated with pre‐existing diabetes.

The American College of Obstetricians and Gynecologists notes that physical activity during pregnancy appears to have benefits for most women and has few risks associated with it, although some adaptation may be required, due to anatomical and physiological changes in pregnancy (ACOG 2015). They recommend that pregnant women have a clinical evaluation prior to starting an exercise programme, to ensure that there are no medical contraindications, and that women be encouraged to participate in aerobic and strength‐conditioning exercises before, during, and after uncomplicated pregnancies.

ACOG 2015 recommends that aerobic exercise during pregnancy is contraindicated in a number of medical conditions, including:

1. cardiac disease;

2. restrictive lung disease;

3. incompetent cervix or cerclage;

4. multiple gestation at risk of preterm birth;

5. persistent second or third trimester bleeding;

6. placenta praevia after 26 weeks' gestation;

7. preterm labour (current pregnancy);

8. ruptured membranes;

9. pre‐eclampsia or pregnancy‐induced hypertension;

10. severe anaemia.

ACOG 2015 considers these activities safe to continue with, or initiate during an uncomplicated pregnancy, following medical advice:

1. walking;

2. swimming;

3. stationary cycling;

4. low‐impact aerobics;

5. modified yoga (avoiding positions that result in decreased venous return);

6. modified Pilates;

7. racquet sports;

8. running or jogging;

9. strength training.

However, running, jogging, or strength training should be undertaken only after consultation with an obstetrical care provider (ACOG 2015). During pregnancy, the duration, frequency, and intensity of physical activity may have to be modified (Nascimento 2012).

ACOG 2015 recommends avoiding these activities during pregnancy:

1. contact sports (e.g. ice hockey, soccer, boxing);

2. activities with a high risk of falling (e.g. skiing, surfing, off‐road cycling);

3. scuba diving;

4. sky diving;

5. 'hot yoga' or 'hot Pilates'.

How the intervention might work

Physical activity may improve glycaemic control in those with types 1 and 2 diabetes because of the interaction between insulin sensitivity and the uptake of glucose by skeletal muscles (Asano 2014). Skeletal muscle takes glucose from the blood using a membrane transporter; improved insulin sensitivity following regular physical activity can increase the efficiency of this transport mechanism (Chibalin 2000; Dela 1993; Hjeltnes 1998).

Why it is important to do this review

Pre‐existing diabetes during pregnancy is associated with short‐ and long‐term adverse effects for the woman and her infant. Identifying interventions to improving health outcomes for women with diabetes and their infants is a priority, as rates of diabetes continue to increase. Exercise has been shown to have benefits for non‐pregnant individuals with pre‐existing type 2 diabetes, such as improving glycaemic control, and reducing visceral adipose tissue (fat tissue located deep in the abdomen and around internal organs) and plasma triglycerides (fatty molecules found in the blood; Thomas 2006). The benefits and safety for a woman during pregnancy and for her baby remains unclear.