This updated review published in 2021 followed the criteria and outcomes used in the review published in 2015. 

For the review published in 2015 there were some differences between published protocol (Brown 2015) as detailed below.

The title was listed as Myo‐inositol for preventing gestational diabetes in our published protocol but we have edited this to Antenatal dietary supplementation with myo‐inositol in women during pregnancy for preventing gestational diabetes in order to allow more clarity around the intervention, population and outcome.

Methods/criteria for considering studies for this review

Types of interventions: we have expanded this section to include myo‐inositol in a combination preparation; this is also reflected in our list of planned subgroup analyses.

Types of participants: we have clarified that participants will be pregnant women rather than pregnant women at risk of gestational diabetes.

We have incorporated the use of GRADE to assess the quality of the body of evidence and have included summary of findings tables; this was not pre‐specified in our published protocol.

We have reported on the outcome need for supplementary insulin therapy; whilst this is not listed in our methods and outcomes section (and was not pre‐specified in our published protocol), we report on this outcome for interest.

Following a consultative process with Professor Caroline Crowther, Dr Julie Brown, Dr Philippa Middleton, Emily Bain, and Tineke Crawford, a core set of primary and secondary outcomes for GDM systematic reviews and core outcomes for GRADE assessment for GDM systematic reviews were drawn up. This has resulted in a number of changes detailed below. These core outcomes were agreed upon after this review had been submitted for peer review.

Additionally, as this is a review on the use of a dietary supplement as an intervention, adverse effects of the intervention has been added as an outcome.

Previous maternal primary outcomes listed in protocol

• Incidence of gestational diabetes (diagnostic criteria as defined in individual studies)

• Pre‐eclampsia

• Caesarean section

Updated maternal primary outcomes used in review

• Gestational diabetes

• Hypertensive disorders of pregnancy (including pre‐eclampsia, eclampsia, pregnancy‐induced hypertension)

Previous neonatal primary outcomes listed in protocol

• Large‐for‐gestational age (birthweight greater than the 90th centile; or as defined by individual study)

• Perinatal mortality

• Death or morbidity composite (variously defined by studies, e.g. infant death, shoulder dystocia, bone fracture or nerve palsy)

Updated neonatal primary outcomes used in review

• Large‐for‐gestational age (birthweight greater than the 90th centile; or as defined by individual study)

• Perinatal mortality (stillbirth and neonatal mortality)

• Mortality or morbidity composite (variously defined by studies, e.g. infant death, shoulder dystocia, bone fracture or nerve palsy)

Previous maternal secondary outcomes listed in protocol

• Postnatal weight retention

• Body mass index (BMI)

• Development of type 1 diabetes mellitus

• Development of type 2 diabetes mellitus

• Impaired glucose tolerance (as defined in individual studies)

• Insulin sensitivity (as defined in individual studies)

• Incidence of pregnancy hyperglycaemia not meeting gestational diabetes diagnostic criteria (diagnostic criteria as defined in individual studies)

• Induction of labour

• Perineal trauma

• Weight gain during pregnancy

• Adiponectin levels

• Gestational age at screening for gestational diabetes

• Postpartum hemorrhage

• Postpartum infection

• Placental abruption

• Polyhydramnios

• Compliance with treatment

• Breastfeeding at discharge, six weeks' postpartum

• Women’s sense of well‐being and quality of life (as defined in individual studies)

• Women’s view of intervention

Updated maternal secondary outcomes used in review

• Caesarean section

• Placental abruption

• Induction of labour

• Perineal trauma

• Postpartum hemorrhage

• Postpartum infection

• Weight gain during pregnancy

• Adherence to the intervention (as defined by trialists)

• Behaviour changes associated with the intervention (as defined by trialists)

• Relevant biomarker changes associated with the intervention (e.g. adiponectin, free fatty acids, triglycerides, high density lipoproteins, low density lipoproteins, insulin)

• Sense of well‐being and quality of life

• Views of the intervention

• Breastfeeding (e.g. at discharge, six weeks postpartum)

• Adverse effects of intervention

Long‐term maternal outcomes

• Postnatal depression

• Postnatal weight retention or return to pre‐pregnancy weight

• Body mass index (BMI)

• Gestational diabetes in a subsequent pregnancy

• Type 1 diabetes mellitus

• Type 2 diabetes mellitus

• Impaired glucose tolerance

• Cardiovascular health (as defined by trialists, including blood pressure (BP), hypertension, cardiovascular disease, metabolic syndrome)

Previous neonatal secondary outcomes listed in protocol

• Macrosomia (as defined in individual studies)

• Birthweight and z‐score

• Head circumference and z‐score

• Length and z‐score

• Small‐for‐gestational age (as defined in individual studies)

• Neonatal hypoglycaemia requiring treatment (as defined in individual studies)

• Gestational age at birth

• Preterm birth (less than 37 weeks’ gestational age)

• Shoulder dystocia

• Bone fracture

• Nerve palsy

• Respiratory distress syndrome

• Hyperbilirubinaemia requiring treatment (as defined in individual studies)

• Apgar scores (less than seven at five minutes)

• Ponderal index

• Fetal adiposity (as defined in individual studies)

• Neonatal glucose concentration

• Infant mortality (fetal, neonatal, perinatal)

Updated secondary outcomes used in review

• Stillbirth

• Neonatal mortality

• Gestational age at birth

• Preterm birth (less than 37 weeks' gestation and less than 32 weeks' gestation)

• Apgar score (less than seven at five minutes)

• Macrosomia

• Small‐for‐gestational age

• Birthweight and z‐score

• Head circumference and z‐score

• Length and z‐score

• Ponderal index

• Adiposity

• Shoulder dystocia

• Bone fracture

• Nerve palsy

• Respiratory distress syndrome

• Hypoglycaemia (variously defined)

• Hyperbilirubinaemia

Previous childhood outcomes listed in protocol

• Weight

• Height

• Head circumference

• Body mass index

• Adiposity (fat mass/fat free mass (variously measured))

• Blood pressure

• Impaired glucose tolerance (as defined in individual studies)

• Development of type 1 diabetes mellitus

• Development of type 2 diabetes mellitus

• Insulin sensitivity

• Dyslipidaemia or metabolic syndrome

• Neurodisability

• Educational achievement

Updated childhood outcomes used in review

• Weight and z scores

• Height and z scores

• Head circumference and z scores

• Adiposity (e.g. as measured by BMI, skinfold thickness)

• Blood pressure

• Type 1 diabetes mellitus

• Type 2 diabetes mellitus

• Impaired glucose tolerance

• Dyslipidaemia or metabolic syndrome

• Neurodisability

• Educational achievement

Previous adulthood outcomes listed in protocol

• Weight

• Height

• BMI

• Adiposity (fat mass/fat‐free mass (variously measured))

• Blood pressure

• Impaired glucose tolerance (as defined in individual studies)

• Development of type 1 diabetes

• Development of type 2 diabetes

• Insulin sensitivity (as defined in individual studies)

• Dyslipidaemia or metabolic syndrome

• Educational achievement

Updated adulthood outcomes used in review

• Weight

• Height

• Adiposity (e.g. as measured by BMI, skinfold thickness)

• Cardiovascular health (as defined by trialists, including BP, hypertension, cardiovascular disease, metabolic syndrome)

• Type 1 diabetes mellitus

• Type 2 diabetes mellitus

• Impaired glucose tolerance

• Dyslipidaemia or metabolic syndrome

• Employment, education and social status/achievement

Previous health services cost outcomes listed in protocol

• Number of hospital visits or health professional visits (e.g. midwife, obstetrician, physician, dietitian)

• Antenatal visits for mother

• Direct costs to families in relation to the management provided

• Length of postnatal stay (mother)

• Admission to neonatal ward/ neonatal intensive care unit

• Length of postnatal stay (baby)

• Cost of maternal care

• Cost of offspring care

Updated health services cost outcomes used in review

• Number of hospital or health professional visits (e.g. midwife, obstetrician, physician, dietitian, diabetic nurse)

• Number of antenatal visits or admissions

• Length of antenatal stay

• Neonatal intensive care unit admission

• Length of postnatal stay (mother)

• Length of postnatal stay (baby)

• Costs to families associated with the management provided

• Costs associated with the intervention

• Cost of maternal care

• Cost of offspring care

Previous GRADE outcomes listed in protocol

• Incidence of gestational diabetes (diagnostic criteria as defined in individual studies)

• Pre‐eclampsia

• Mode of birth

• Large‐for‐gestational age (birthweight greater than the 90th centile; or as defined by individual study)

• Perinatal mortality

• Fetal adiposity

• Impaired glucose tolerance as child/adult

Updated GRADE outcomes used in review

Maternal

• Diagnosis of gestational diabetes

• Gestational weight gain

• Hypertensive disorders of pregnancy (including pre‐eclampsia, eclampsia, pregnancy‐induced hypertension)

• Caesarean Section

• Perineal trauma

• Postnatal depression

• Development of subsequent type 2 diabetes mellitus

Offspring (infant, child, adult)

• Large‐for‐gestational age

• Perinatal mortality (stillbirth and neonatal mortality)

• Composite of serious neonatal outcomes

• Neonatal hypoglycaemia (variously defined)

• Offspring adiposity (e.g. as measured by BMI, skinfold thickness)

• Offspring diabetes

• Neurosensory disability