Design

All of the included trials were parallel randomised controlled trials (RCTs).

Sample sizes

Sample sizes ranged from a minimum of six women (Ramos 2015) to a maximum of 180 women (Youngwanichsetha 2014). Only the Youngwanichsetha 2014 trial had a sample size of more than 100 women.

Setting

All trials were conducted in middle‐ or high‐income countries. Three trials were conducted in the USA (Avery 1997; Bung 1991; Jovanovic‐Peterson 1989) and in Brazil (Bambicini 2012; de Barros 2010; Ramos 2015), two trials in Canada (Adam 2014; Brankston 2004), and one trial each in Italy (Bo 2014), Australia (Halse 2014) and Thailand (Youngwanichsetha 2014). One trial was conducted in the 1990s (Bung 1991) and two trials in the 2000s (Bo 2014; de Barros 2010). For the remaining trials (Adam 2014; Avery 1997; Bambicini 2012; Brankston 2004; Halse 2014; Jovanovic‐Peterson 1989; Ramos 2015; Youngwanichsetha 2014), no details were provided regarding timing of the trial.

Participants

All trials recruited pregnant women with a diagnosis of gestational diabetes mellitus (GDM).

Interventions and comparisons

The exercise interventions and comparisons were very varied and included the following.

1. A supervised, individualised follow‐up with a kinesiologist versus standard counselling for physical activity (Adam 2014).

2. Exercise using a cycle ergometer for 30 minutes duration, three to four times per week including both supervised and unsupervised sessions versus standard care with no additional exercise programme (Avery 1997). No details on the duration of the programme.

3. Aerobic activity (30 minutes brisk walking) or resistance exercises (30‐minutes circuit workout with elastic‐band exercises) versus a control group who remained seated for 30 minutes listening to explanations about Shantala exercises for the baby (Bambicini 2012).

4. All women were given an individually‐prescribed diet (carbohydrates 48% to 50%, proteins 18% to 20%, fats 30% to 35%, fibre 20% to 25 g/day, no alcohol). Women in the exercise intervention group were advised to walk briskly at least 20 minutes/day. Women in the behaviour group were given individual oral/written recommendations for helping with healthy dietary choices (i.e. lowering carbohydrate intake, strategies for out‐of‐home eating, healthy cooking and food shopping and related behavioural suggestions), and debunking false myths about diet in pregnancy and women in the control group who were given individually‐prescribed dietary recommendations only (n = 50) (Bo 2014). This study also included a combined behaviour and exercise group that was not included in this review.

5. The intervention group undertook a progressive physical conditioning program involving three supervised introductory sessions, and weekly contact with supervisor. Women were instructed to perform resistance training circuit‐type exercises three times per week. Women were instructed to exercise at a level that felt “somewhat hard”, and were taught to monitor their heart rate to ensure that it did not rise above 140 beats/min during exercise. All exercise sessions were recorded in a log book (n = 16). The control group received standard diabetic diet advice: 40% carbohydrate, 20% protein, 40% fat, calculated at 24 kcal/kg to 30 kcal/kg per day on the basis of the woman’s ideal pre‐pregnant body weight. Women were asked not to begin a structured exercise program for the remainder of the pregnancy (Brankston 2004).

6. The intervention group was provided with dietary advice and instructed to conduct a non‐sedentary lifestyle, and attend the exercise laboratory three times a week to exercise under medical supervision. Exercise was 45 minutes with two, five‐minute breaks, on a recumbent bicycle, at 50% of their last determined maximum aerobic capacity (classed as moderate exercise) versus standard care insulin therapy and diet (Bung 1991).

7. All women received dietary advice from a nutritionist. The program consisted of a circuit of eight resistance training exercises using an elastic band to work the main muscle groups (chest, back, biceps, triceps, deltoid, quadriceps, thigh and calf muscles). Women were instructed to perform 15 repetitions of each exercise three times a week (once a week under supervision in the clinic, and twice a week at home) from recruitment (between 24 and 34 weeks) until the end of gestation. Women were instructed to exercise at a "somewhat heavy" intensity. Women were contacted by telephone at least once a week to verify adherence to the program (n = 32). The control group received usual care, and were questioned as to whether they had started some type of physical activity (N = 32) (de Barros 2010).

8. In addition to usual care, the intervention group took part in five sessions per week of a home‐based exercise program (three supervised and two unsupervised) on an upright stationary cycle ergometer (continuous moderate intensity cycling, with intervals of varying intensity consisting of 15 to 60 seconds of higher intensity bouts every two minutes, interspersed with lower‐intensity recovery pedalling in between, tailored to a percentage of the woman's age‐predicted maximum heart rate). The intervention commenced at recruitment (between 26 and 30 weeks' gestation) until 34 weeks of gestation (n = 20). The comparison group had usual care (n = 20), which consisted of assessment of glycaemic control and counselling by a diabetes educator and dietician, and self‐monitoring of fasting and 120‐minute postprandial glucose levels (n = 20) (Halse 2014).

9. In addition to usual care, women in the intervention group participated in a six‐week exercise program that consisted of 20 minutes of supervised aerobic training on an arm ergometer, sufficient to maintain target heart rate in a training range (n = 10). The control group was managed with a standard diet consisting of 40% carbohydrate, 20% protein, and 40% fat calculated at 24 kcal/kg to 30 kcal/kg/24 hours of present pregnant weight, divided into three meals and three snacks. Women in the control group did not participate in any structured exercise program (n = 9) (Jovanovic‐Peterson 1989).

10. A 10‐week program of regular aerobic exercise of three 50‐minute sessions per week (no further details) (n = 2), versus 10 weeks of a 50‐minute stretching and relaxation session once a week (n = 4) (Ramos 2015).

11. Training in mindfulness eating, and yoga exercise in two 50‐minute sessions. Participants were provided with manuals and encouraged to continue mindfulness eating and yoga exercise at home five times a week for eight weeks (n = 90) versus standard diabetes care (n = 90) (Youngwanichsetha 2014).

Outcomes

Two trials reported hypertensive disorders of pregnancy (pre‐eclampsia) ‐ Avery 1997; Jovanovic‐Peterson 1989.

Five trials reported caesarean section ‐ Avery 1997; Bo 2014; Bung 1991; de Barros 2010; Halse 2014.

One trial reported perinatal mortality (stillbirth and neonatal mortality) ‐ Jovanovic‐Peterson 1989.

Two trials reported a mortality or morbidity composite ‐ Bo 2014; Jovanovic‐Peterson 1989.

Seven trials reported the use of additional pharmacotherapy ‐ Adam 2014; Avery 1997; Bo 2014; Brankston 2004; de Barros 2010; Halse 2014; Jovanovic‐Peterson 1989.

One trial reported maternal hypoglycaemia ‐ Bung 1991.

Five trials reported glycaemic control during/end of treatment ‐ Bo 2014; Bung 1991; Brankston 2004; Jovanovic‐Peterson 1989; Youngwanichsetha 2014.

Three trials reported weight gain in pregnancy ‐ Adam 2014; de Barros 2010; Halse 2014.

One trial reported adherence to the intervention ‐ Jovanovic‐Peterson 1989.

One trial reported induction of labour ‐ Halse 2014.

Two trials reported maternal mortality ‐ Avery 1997; Jovanovic‐Peterson 1989.

One trial reported on views of the intervention ‐ Halse 2014.

Three trials reported postnatal weight retention or return to pre‐pregnancy weight (maternal BMI at follow‐up) ‐ Bo 2014; de Barros 2010; Halse 2014.

One trial reported stillbirth ‐ Avery 1997.

Five trials reported macrosomia ‐ Avery 1997; Bo 2014; Bung 1991; de Barros 2010; Jovanovic‐Peterson 1989.

Four trials reported gestational age at birth ‐ Avery 1997; Bung 1991; de Barros 2010; Halse 2014.

Five trials reported preterm birth ‐ Avery 1997; Bo 2014; de Barros 2010; Halse 2014; Jovanovic‐Peterson 1989.

One trial reported five‐minute Apgar < seven ‐ Bung 1991.

Six trials reported birthweight ‐ Avery 1997; Bung 1991; de Barros 2010; Halse 2014; Jovanovic‐Peterson 1989; Ramos 2015.

One trial reported length at birth ‐ Bung 1991.

One trial reported neonatal hypoglycaemia ‐ Bung 1991.

One trial reported respiratory distress syndrome ‐ Bung 1991.

One trial reported hyperbilirubinaemia ‐ Bung 1991.

One trial reported hypocalcaemia ‐ Bung 1991.

No data were reported in the included trials for any of the other pre‐specified outcomes for this review listed below.

For the mother: placental abruption, postpartum haemorrhage, postpartum infection, perineal trauma/tearing, breastfeeding at discharge, six weeks postpartum, six months or longer, sense of well‐being and quality of life, behavioural changes associated with the intervention, relevant biomarker changes associated with the intervention, postnatal depression, postnatal weight retention or return to pre‐pregnancy weight, BMI, GDM in a subsequent pregnancy, type 2 diabetes, impaired glucose tolerance, cardiovascular health.

For the infant: neurosensory disability, small‐for‐gestational age, birth trauma (shoulder dystocia, bone fracture, nerve palsy), birthweight z score, head circumference and z score, length and z score, ponderal index, neonatal adiposity, polycythaemia, relevant biomarker changes associated with the intervention, childhood weight and z scores, height and z scores, head circumference and z scores, adiposity, educational attainment, blood pressure, type 1 diabetes, type 2 diabetes, impaired glucose tolerance, dyslipidaemia or metabolic syndrome.

For the child as an adult: weight, height, adiposity, cardiovascular health, employment, education and social status/achievement, type 1 diabetes, type 2 diabetes, impaired glucose tolerance.

Health service outcomes: number of antenatal visits or admissions, number of hospital or health professional visits, admission to neonatal intensive care unit/nursery, cost of maternal care, cost of offspring care, costs associated with the intervention, costs to families associated with the management provided, cost of dietary monitoring, costs to families, extra use of healthcare services, women’s view of treatment advice, duration of stay in neonatal intensive care unit or special care baby unit and duration of maternal and neonatal hospital stay.

Declarations of interest in the trial reports

Four publications clearly stated that there were no conflicts of interest (Adam 2014; Bo 2014; Halse 2014; Ramos 2015). Seven publications did not provide details on conflicts of interest (Avery 1997; Bambicini 2012; Brankston 2004; Bung 1991; de Barros 2010; Jovanovic‐Peterson 1989; Youngwanichsetha 2014).

Sources of trial funding

Three publications declared funding sources, none of which were associated with the pharmaceutical industry (Bo 2014; de Barros 2010; Halse 2014). One trial (Avery 1997) reported funding sources from multiple sources (academic, governmental and other) that also included funding from Boehringer Manheim Corporation. The type of funding from Boehringer Manheim Corporation was unclear. No details on sources of funding were provided by seven publications (Adam 2014; Bambicini 2012; Brankston 2004; Bung 1991; Jovanovic‐Peterson 1989; Ramos 2015; Youngwanichsetha 2014).

Studies awaiting classification

One study remains in Characteristics of studies awaiting classification (Frias 2012). ClinicalTrials.gov stated this trial has been terminated due to recruitment issues. We will attempt to contact the responsible party for further information.

Random sequence generation

Four trials were judged to be of low risk of bias. Avery 1997, Bo 2014, Brankston 2004 and de Barros 2010 reported using computer‐generated random number tables.

Seven trials were judged as unclear risk of bias due to lack of methodological details (Adam 2014; Bambicini 2012; Bung 1991; Halse 2014; Jovanovic‐Peterson 1989; Ramos 2015; Youngwanichsetha 2014).

Allocation concealment

Three trials were judged to be of low risk of bias. Brankston 2004, de Barros 2010 and Halse 2014 reported using sequentially numbered, opaque envelopes.

Eight trials were judged as unclear risk of bias due to lack of methodological details (Adam 2014; Avery 1997; Bambicini 2012; Bo 2014;Bung 1991; Jovanovic‐Peterson 1989; Ramos 2015; Youngwanichsetha 2014).

Performance bias

Eight trials were judged as unclear risk of bias due to lack of methodological details (Adam 2014; Bambicini 2012; Bo 2014; Bung 1991; Halse 2014; Jovanovic‐Peterson 1989; Ramos 2015; Youngwanichsetha 2014). Bo 2014 reported that women were not blinded but dieticians and obstetricians who reported maternal/neonatal complications, and the laboratory personnel were blinded to the group assignment.

Three trials were judged as high risk of bias as they stated that the participants were not blinded (Avery 1997; Brankston 2004; de Barros 2010).

Detection bias

Two trials were judged to be of low risk of bias. Bo 2014 reported that outcome assessors including dietitians, obstetricians and laboratory personnel were blinded to allocation. de Barros 2010 also stated that obstetricians recording data were blinded to group allocation.

Nine trials were judged as unclear risk of bias due to lack of methodological details (Adam 2014; Avery 1997; Bambicini 2012; Brankston 2004; Bung 1991; Halse 2014; Jovanovic‐Peterson 1989; Ramos 2015; Youngwanichsetha 2014).

Primary outcomes

Mother

Neonatal/infant

Secondary outcomes

Mother

Neonatal/infant