|Methods||Randomised controlled trial.|
|Participants||N = 92.|
Women aged at 18–45 years, diagnosed with GDM by a 75 g OGTT between 20 and 32 weeks' gestation according to ADIPS criteria (see notes), with an otherwise healthy singleton pregnancy.
Exclusion criteria: women who had special dietary requirements (including vegetarianism/veganism), pre-existing diabetes, or pregnancy achieved by assisted reproduction and those who smoked or consumed alcohol during pregnancy.
|Interventions||Low-GI diet group (n = 50): diet GI target of ≤ 50, other nutrients were the same as the comparison group.|
High-fibre moderate-GI diet (n = 49): diet GI target of around 60, which represented average GI of Australian population.
healthy diets of similar protein (15% to 25% total daily energy intake), fat (25% to 30% total daily energy intake), and carbohydrate (40% to 45% total daily energy intake) content;
completed 3-day food record (2 weekdays and 1 weekend day) at baseline and 36-37 weeks' gestation;
received 2 food model booklet to assist in portion size estimation.
|Outcomes||Pregnancy outcomes: birthweight, the need for emergency caesarean section, gestational age at birth, macrosomia, SGA, LGA, ponderal index, neonatal anthropometry (length, head circumference), maternal metabolic profile in GDM.|
68% participants in this trial had a BMI < 25 kg/m2.
Insulin treatment was commenced if the mean fasting BGL or 1-h postprandial BGL in the preceding week exceeded 5.2 and 7.5 mmol/L, respectively.
Self-reported pre-pregnancy weight; last weight before delivery was obtained from medical record.
ADIPS criteria used for GDM diagnosis:
fasting BGL ≥ 5.5 mmol/L;
2-hour BGL after 75 g glucose load ≥ 8.0 mmol/L;
1 or more value(s) is (are) met or exceeded.
|Risk of bias|
|Bias||Authors' judgement||Support for judgement|
|Random sequence generation (selection bias)||Low risk||Described as "the enrolled subjects were centrally randomised to study diet by computer generated random numbers, stratified by BMI and weeks of gestation".|
|Allocation concealment (selection bias)||Low risk||Described as "the allocation sequence was unpredictable and concealed from the recruiter".|
|Blinding of participants and personnel (performance bias) |
|Low risk||Reported that (besides research dietitian who provided trial intervention) all study personnel and participants were blinded to dietary assignment.|
|Blinding of outcome assessment (detection bias) |
|Unclear risk||Reported that the unblinded research dietitian was involved in data collection, no other information on whether or not other outcome assessors were blinded to group allocation.|
|Incomplete outcome data (attrition bias) |
|Low risk||In the low-GI group, 1 woman was excluded due to incorrect GDM diagnosis, 3 women withdraw after intervention, 2 women had preterm births, leaving 44 women who completed the study, and 47 women were included in analysis.|
In high-fibre group, 2 women withdrew after group allocation, another 2 women withdrew after intervention; 2 women had preterm births, leaving 43 women who completed the study and 45 women who were included in analysis.
|Selective reporting (reporting bias)||High risk||Only limited data were reported on some of the prespecified review outcomes.|
|Other bias||High risk||At baseline, 2-hour post 75 g glucose load BGL for women in low-GI group were significantly higher than those in conventional high-fibre group (mean [SD]: low-GI 8.6 [1.2] mmol/L vs high-fibre group 8.0 [1.3] mmol/L; P = 0.024).|