Table 2. Maternal Outcomes.
| Outcome | No./total (%)a | Risk difference (95% CI) | Relative risk (95% CI) | P value | |
|---|---|---|---|---|---|
| Early metformin (n = 264) | Placebo (n = 262) | ||||
| Primary outcome b | |||||
| Primary composite outcome | 150/264 (56.8) | 167/262 (63.7) | −6.9% (−15.1% to 1.4%) | 0.89 (0.78 to 1.02) | .13 |
| Initiation of insulin only | 101/263 (38.4) | 134/262 (51.1) | −12.7% (−21.2% to −4.3%) | 0.75 (0.62 to 0.91) | .004 |
| Fasting glucose at wk 32, mean (SD), mmol/L | 4.9 (0.5) | 5.0 (0.5) | −0.1 (−0.19 to −0.01) | .03 | |
| Fasting glucose at wk 38, mean (SD), mmol/L | 4.5 (0.4) | 4.7 (0.5) | −0.2 (−0.28 to −0.09) | <.001 | |
| Secondary outcomes | |||||
| Time to insulin initiationc | .001 | ||||
| Mode of delivery | |||||
| Cesarean delivery | 114/262 (43.5) | 100/262 (38.2) | 5.2% (−3.1% to 13.7%) | 1.14 (0.93 to 1.4) | .40 |
| Induced delivery | 75/262 (28.6) | 88/262 (33.2) | −4.6% (−12.5% to 3.3%) | 0.86 (0.67 to 1.11) | |
| Spontaneous delivery | 73/262 (27.9) | 75/262 (28.6) | −0.7% (−8.5% to 6.9%) | 0.97 (0.74 to 1.28) | |
| Emergency cesarean | 53/114 (46.5) | 53/100 (53) | −6.5% (−13.9% to 12.9%) | 0.99 (0.74 to 1.32) | 1 |
| Elective cesarean | 61/114 (53.5) | 47/100 (47) | |||
| Preterm birth (<37 wk) | 24/261 (9.2) | 17/260 (6.5) | 2.8% (−2.0% to 7.3%) | 1.41 (0.78 to 2.56) | .33 |
| Hemoglobin A1C at wk 38, mean (SD), mmol/mol | 33.9 (3.4) | 35.0 (3.9) | −1.1% (−1.79 to −0.34) | .004 | |
| Insulin dose required, mean (SD), IU | 20.4 (19.8) | 24.2 (22.8) | −3.8 (−9.3 to 1.7) | .17 | |
| Maternal weight change randomization to delivery, mean (SD), kg | 0.8 (3.3) | 2.0 (3.6) | −1.2 (−1.99 to −0.42) | .003 | |
| Maternal weight change randomization to wk 12 postpartum, mean (SD), kg | −5.9 (4.4) | −5.1 (4.9) | −0.8 (−1.64 to 0.06) | .07 | |
| Treatment satisfaction | 173/227 (76.2) | 159/237 (67.1) | 9.1% (1.0% to 17.0%) | .04 | |
| Maternal morbidityd | |||||
| Gestational hypertension | 31/262 (11.8) | 28/262 (10.6) | 1.2% (−4.2% to 6.6%) | 1.11 (0.69 to 1.8) | .77 |
| Preeclampsia | 10/262 (3.8) | 5/262 (1.9) | 1.9% (−0.9% to 4.8%) | 2.01 (0.7 to 5.79) | .29 |
| Antepartum hemorrhage | 15/262 (5.7) | 27/262 (10.3) | −4.6% (−9.2% to 0.1%) | 0.56 (0.3 to 1.02) | .08 |
| Postpartum hemorrhage | 51/262 (19.5) | 63/262 (24.0) | −4.5% (−11.6% to 2.5%) | 0.81 (0.59 to 1.12) | .24 |
| Any bleeding | 60/262 (22.9) | 80/262 (30.5) | −7.6% (−15.2% to −0.1%) | 0.75 (0.56 to 1.0) | .06 |
Conventional unit conversion factor: to convert glucose to mg/dL, divide by 0.0555.
Numeric values are reported as No./total (%) unless otherwise indicated.
The composite primary outcome was achieved if a participant initiated insulin treatment during the period between randomization and delivery or had a measured fasting glucose level of at least 5.1 mmol/mol at 32 weeks’ gestation or at 38 weeks’ gestation.
Only a P value is shown for this row because it is not possible to calculate average or median survival times due to the censoring in the distribution (eg, the time to insulin would be censored at the delivery date for more than 50% of the metformin group).
Other outcomes related to maternal morbidity are detailed in eTable 2 in Supplement 2.