| Study | Reason for exclusion |
|---|---|
| Austria 1994 | Not a randomised trial; cross‐over design and comparison of different ways of measuring blood glucose. Participants: 500 women having an OGTT, usually at 24 to 28 weeks' gestation, but some earlier and a few later or postpartum. |
| Austria 1998 | Cross‐over study of response to different glucose loads in those with a diagnosis of GDM and those without. Participants: 60 women, 30 with GDM and willing to undergo a second GTT and 30 healthy pregnant women. Interventions: 75 g OGTT vs 100 g OGTT. |
| Canada 1999 | Wrong intervention: routine screening of all women vs selective screening for clinical indications of GDM. Participants: 2401 low‐risk women randomly assigned to screening, or screening only if a clinical indication arose during pregnancy. Interventions: routine screening with 50 g OGTT vs screening with 100 g OGTT only if indicated. Outcome: macrosomia rate. |
| Canada 2005 | Outcomes reported as percentage rates. Participants: 5489 women. Interventions: 50 g OGTT and 100 g OGTT vs 50 g OGTT and 75 g OGTT vs 75 g OGTT. Canada 2010 subset of Canada 2005. Outcomes: economic evaluation of 1‐step and 2‐step screening and diagnostic approaches, no evaluation of maternal and infant outcomes. Participants: 1594 women. Intervention: as above. |
| China 1995 | Not a randomised trial; women 'randomly selected' for a 50 g OGTT. Participants: 220 women in the third trimester. Interventions: comparison of capillary vs venous blood samples. |
| China 1995a | Not a randomised trial. Participants: 622 women at 28 to 32 weeks. Interventions: 50 g OGTT if results > 7.78 mmol/L, then 75 g OGTT. |
| Germany 2004 | Cross‐over trial; no clinical outcomes reported. Participants: 34 women at around 30 weeks' gestation, unselected. Interventions: low‐ vs high‐carbohydrate diet before OGTT. |
| Greece 2004 | Not a randomised trial: 2 groups matched for key characteristics. No clinical outcomes reported. Participants: 47 women undergoing 100 g OGTT at 24 to 28 weeks. Interventions: fingertip vs forearm blood sample. |
| Hong Kong 1993 | Cross‐over trial; participants randomly assigned to the order in which they were given 50 g and 75 g OGTT. Participants: 50 women at 28 to 32 weeks' gestation. Interventions: 50 g OGTT and 75 g OGTT. |
| Iran 2007 | Cross‐over trial. Participants: 141 women at 24 to 28 weeks' gestation if low risk. Interventions: breakfast containing 50 g simple glucose vs 50 g glucose challenge. |
| Iran 2008 | Cross‐over trial. Participants: 138 women. Intervention: 50 g OGTT vs breakfast (includes 50 g sugar or jam). |
| Ireland 2000 | Wrong intervention. Universal screening vs selective screening. Participants: 3742 women at booking visit. Interventions: universal vs selective screening for GDM. |
| Ireland 2014a | Trial comparing identification of gestational diabetes using OGTT in primary and secondary care settings. |
| New Zealand 1984a | Cross‐over trial; 2 studies reported in the same paper. Participants: 26 women; consecutive referrals for carbohydrate tolerance testing because of risk factors for GDM. Interventions: 50 g OGTT vs 50 g glucose polymer tolerance test. |
| New Zealand 1984b | Cross‐over trial; 2 studies reported in the same paper. Participants: 20 women; consecutive referrals for carbohydrate tolerance testing because of features suggestive of GDM. Interventions: 50 g glucose polymer vs 50 g glucose. |
| Singapore 1992 | Cross‐over trial. Participants: 56 women in the third trimester. Interventions: 50 g OGTT vs 75 g OGTT. |
| Thailand 1995 | Not a randomised trial. Participants: 709 women. Interventions: 50 g OGTT and 75 g OGTT within a week, then 100 g if 50 g OGTT blood sugar ≥ 7.8 within a week of the 75 g OGTT. |
| Thailand 2003 | Cross‐over trial. Participants: 42 women with a positive 50 g glucose challenge test at 14 to 36 weeks. Interventions: 75 g OGTT vs 100 g OGTT. |
| Thailand 2008 | Participants known to have normal glucose tolerance. Participants: 41 women with normal 100 g OGTT and 25 women with normal 75 g OGTT. Interventions: 75 g vs 100 g OGTT ‐ postload blood glucose levels. |
| Tunisia 2001 | Cross‐over trial. Participants: 100 women at 24 to 28 weeks. Interventions: meal and 50 g oral glucose as screening for GDM. |
| USA 1989 | Quasi‐randomised study using alternate allocations. Also, cross‐over design and 42% lost to follow‐up. Participants: 114 women ≤ 24 weeks' gestation. Interventions: 50 g vs 100 g OGTT. |
| USA 1991 | Quasi‐randomised study using alternate allocations and a cross‐over design. Participants: 37 women at 10 to 38 weeks' gestation. Interventions: 50 g OGTT if result ≥ 135 mg/dL, then 3‐day diet of > 150 g/d of CHO, then > 1 week of normal diet before 50 g OGTT or > 1 week of normal diet plus 3‐day diet of > 150 g/d of CHO before 50 g OGTT. |
| USA 1993a | Cross‐over trial; published as abstract only. Participants: 45 women with an abnormal glucose challenge screening test. Interventions: '3‐hour standard' OGTT vs intravenous GTT. |
| USA 1993b | Cross‐over trial. Participants: 26 low‐risk women at 28 to 32 weeks' gestation. Interventions: non‐fasting OGTT vs fasting OGTT. |
| USA 1993c | Not a randomised trial. Case series in which all women were given both tests. Participants: 32 women at 26 to 36 weeks' gestation. Interventions: 75 g OGTT vs 100 g OGTT. |
| USA 1995 | Not a randomised trial, cross‐over design. Participants: 32 women at 26 to 36 weeks' gestation. Interventions: 100 g then 75 g OGTT. |
| USA 1995a | Outcomes data reported by whether or not the women had GDM, not by allocated group. Participants: 80 women with a positive 50 g glucose challenge test. Interventions: 75 g OGTT vs 50 g OGTT. |
| USA 1999 | Cross‐over trial. Participants: 160 women at 24 to 28 weeks' gestation. Interventions: 30 jelly beans vs 50 g glucose drink. |
| USA 2001 | Participants were women with a diagnosis of gestational diabetes. |
| USA 2015 | Brieft abstract only. Participants: women with increased BMI (> 25) at 16 weeks' gestation. Intervention: early testing of glucose intolerance and provision of an intervention to reduce the risk of GDM (prevention intervention). |
BMI: body mass index CHO: carbohydrate GDM: gestational diabetes mellitus GTT: glucose tolerance test OGTT: oral glucose tolerance test vs: versus