Table 1. Study Participant Baseline Characteristics.
| No. (%)a | ||
|---|---|---|
| Metformin plus insulin (n = 397) | Insulin plus placebo (n = 397) | |
| Demographics | ||
| Age, mean (SD), y | 32.8 (5.5) | 33.1 (5.7) |
| Raceb | ||
| American Indian or Alaska Native | 3 (1) | 1 (0) |
| Asian | 10 (3) | 13 (3) |
| Black or African American | 119 (30) | 115 (29) |
| Native Hawaiian or Other Pacific Islander | 2 (1) | 2 (1) |
| White | 55 (14) | 57 (14) |
| ≥ 2 Races | 8 (2) | 2 (1) |
| Not reported or declined to report | 95 (24) | 97 (24) |
| Hispanic ethnicityb | ||
| No | 194 (49) | 188 (47) |
| Yes | 203 (51) | 209 (53) |
| Type of insurance | n = 396 | n = 395 |
| Medicaid, federal, or state insurance | 290 (73) | 292 (74) |
| Private | 77 (19) | 79 (20) |
| Military | 0 | 3 (1) |
| None | 29 (7) | 21 (5) |
| First pregnancy | 66 (17) | 55 (14) |
| Prior birth ≥20 wk | 302 (76) | 296 (75) |
| Diabetes characteristics | ||
| Preexisting type 2 diabetes requiring medical therapy prior to pregnancy | 311 (78) | 313 (79) |
| Diagnosis of diabetes early in pregnancy | 86 (22) | 84 (21) |
| Use of diabetes medication prior to pregnancy | 174 (44) | 181 (46) |
| Metformin used earlier in pregnancy | 162 (41) | 175 (44) |
| Criteria to diagnose diabetes early in pregnancyc | n = 86 | n = 84 |
| HbA1c ≥6.5%d | 25 (29) | 22 (26) |
| Fasting blood glucose ≥126 mg/dL | 5 (6) | 5 (6) |
| 1-h OGTT≥200 mg/dLd | 18 (21) | 24 (29) |
| 2-Step method positive | 25 (29) | 20 (24) |
| 1-Step method positive | 12 (14) | 12 (14) |
| Other clinical characteristics and laboratory results | ||
| Chronic hypertension requiring medication | 103 (26) | 86 (22) |
| Smoking during pregnancy | 28 (7) | 32 (8) |
| Body mass index at enrollmente | n = 383 | n = 379 |
| Mean (SD) | 36.4 (8.0) | 36.3 (8.9) |
| Median (IQR) | 35.2 (31.2-41.1) | 34.4 (29.6-41.5) |
| Distribution | ||
| <30 | 76 (19) | 105 (26) |
| 30 to <40 | 198 (50) | 164 (41) |
| ≥40 | 109 (27) | 110 (28) |
| Gestational age at enrollment, wkf | ||
| 18 to <23 | 162 (41) | 165 (42) |
| <18 | 235 (59) | 232 (58) |
| HbA1c % at enrollmentd | n = 361 | n = 361 |
| Mean (SD) | 7.7 (2.02) | 7.7 (1.97) |
| Median (IQR) | 7.2 (6.0-9.1) | 7.3 (6.1-9.1) |
| Gestational age at HbA1c measurement, mean (SD), wk | 11.1 (4.4) | 10.6 (5.4) |
| Gestational age at HbA1c measurement, median (IQR), wk | 10.3 (7.9-14.1) | 10.3 (7.4-13.7) |
Abbreviations: HbA1c, hemoglobin A1c; OGTT, oral glucose tolerance test.
SI conversion: for glucose to mmol/L, multiply by 0.0555.
a
Data are presented as No. (%) unless otherwise indicated.
b
Race and ethnicity were determined by medical record abstraction or if not in the record, by participant self-report.
c
Subcategories do not sum because data were missing for 2 participants.
d
Reported as %, to convert mmol/mol use (10.93 × HbA1c) − 23.50.
e
Calculated as weight in kilograms divided by height in meters squared.
f
Gestational age determined by menstrual date confirmed by first or second trimester ultrasound, and if menstrual date was missing, by ultrasound alone.