Table 2.
Meta-analysis of randomized controlled trials comparing outcomes from treatment with metformin v insulin in women with gestational diabetes
| Outcomes | No of studies | No of patients treated | Mean difference (95% CI) | Relative risk (95% CI) | P value | I2 value | |
|---|---|---|---|---|---|---|---|
| With metformin | With insulin | ||||||
| Primary outcomes | |||||||
| HbA1c level at end of third trimester (%) | 4 | 508 | 533 | −0.04 (−0.09 to 0.02) | — | 0.21 | 24 |
| Severe maternal hypoglycaemia (%) | 4 | 268 | 268 | — | 0 v 0 | — | — |
| Pre-eclampsia (%) | 5 | 646 | 653 | — | 0.82 (0.56 to 1.20) | 0.32 | 0 |
| Maternal weight gain (kg) | 4 | 468 | 505 | −1.14 (−2.22 to −0.06)* | — | 0.04 | 64 |
| Caesarean section (%) | 6 | 678 | 684 | 0.97 (0.85 to 1.12) | 0.71 | 17 | |
| Gestational age at delivery (weeks) | 6 | 678 | 684 | −0.16 (−0.30 to −0.02) | — | 0.03 | 0 |
| Preterm birth (%) | 5 | 646 | 653 | — | 1.50 (1.04 to 2.16) | 0.03 | 0 |
| Birth weight (g) | 6 | 678 | 684 | −31.4 (−86.5 to 23.6) | — | 0.26 | 4 |
| Macrosomia (%) | 6 | 678 | 684 | — | 0.96 (0.73 to 1.27) | 0.80 | 13 |
| Large for gestational age (%) | 5 | 646 | 653 | — | 0.88 (0.69 to 1.11) | 0.28 | 22 |
| Small for gestational age (%) | 5 | 646 | 653 | — | 0.88 (0.58 to 1.33) | 0.53 | 0 |
| Any neonatal hypoglycaemia (%) | 6 | 676 | 684 | — | 0.78 (0.60 to 1.01) | 0.06 | 0 |
| Perinatal mortality (%) | 4 | 600 | 607 | — | 1.0 (0.14 to 7.12) | 0.99 | 0 |
| Secondary outcomes | |||||||
| Fasting blood glucose (mmol/L) | 4 | 521 | 527 | 0.04 (−0.03 to 0.11) | — | 0.24 | 49 |
| Postprandial blood glucose (mmol/L) | 4 | 521 | 527 | −0.14 (−0.22 to −0.05) | — | 0.002 | 38 |
| Maternal weight gain since entry (kg) | 4 | 565 | 533 | −1.23 (−1.72 to −0.73)* | — | <0.001 | 61 |
| Pregnancy induced hypertension (%) | 3 | 553 | 557 | — | 0.53 (0.31 to 0.90) | 0.02 | 0 |
| Induction (%) | 3 | 520 | 527 | — | 0.91 (0.81 to 1.02) | 0.11 | 46 |
| Cord C peptide (nmol/L) | 0 | — | — | — | — | — | — |
| Cord insulin (pmol/L) | 1 | 220 | 234 | 7.64 (−92.7 to 108) | — | 0.88 | — |
| 1 minute Apgar score <7 (%) | 0 | — | — | — | — | — | — |
| 5 minute Apgar score <7 (%) | 1 | 363 | 370 | — | 3.06 (0.32 to 29.3) | 0.33 | — |
| Obstetric trauma (%) | 2 | 472 | 477 | — | 0.86 (0.45 to 1.63) | 0.64 | 2 |
| Severe neonatal hypoglycaemia† (%) | 3 | 519 | 527 | — | 0.62 (0.42 to 0.94) | 0.02 | 48 |
| Neonatal jaundice (%) | 6 | 677 | 684 | — | 0.90 (0.67 to 1.21) | 0.47 | 0 |
| Neonatal respiratory distress syndrome (%) | 5 | 630 | 634 | — | 1.30 (0.70 to 2.41) | 0.40 | 0 |
| Stillbirth (%) | 5 | 632 | 638 | — | 1.38 (0.27 to 7.02) | 0.69 | 0 |
| Neonatal mortality (%) | 4 | 599 | 606 | — | 0 v 0 | — | — |
| NICU admission (%) | 5 | 631 | 638 | — | 0.87 (0.70 to 1.09) | 0.23 | 0 |
I2=Heterogeneity. HbA1c= glycated haemoglobin. NICU=neonatal intensive care unit.
*Estimated using a random effects model because I2>50%
†Defined by authors or requiring intravenous glucose or NICU admittance.