Table 1.
Baseline characteristics by preconception eGFR (ml/min per 1.73 m2)
| Baseline Characteristics | eGFR ≥90 (N=522,752)a | eGFR 60 to <90 (N=42,543)a | eGFR 45 to <60 (N=479)a | eGFR <45 (N=133)a |
|---|---|---|---|---|
| Unique mothers, N (%) | 430,048 (94) | 39,298 (9) | 460 (0.1) | 122 (0.03) |
| Sociodemographic characteristics, N (%) | ||||
| Age at conception, years, mean±SD | 30±5.2 | 33±5.0b | 33±5.0b | 32±5.1b |
| Period of cohort entry | ||||
| 2007–2011 | 116,511 (22.3) | 8799 (20.7) | 97 (20.2) | 23 (17.3) |
| 2012–2015 | 210,792 (40.3) | 14,514 (34.2) | 168 (35.1) | 55 (41.4) |
| 2016–2019 | 195,449 (37.4) | 19,230 (45.2) | 214 (44.7) | 55 (41.4) |
| Income quintile | ||||
| First (lowest) | 114,792 (22.0) | 7760 (18.2) | 123 (25.7) | 31 (23.3) |
| Second | 106,084 (20.3) | 7899 (18.6) | 93 (19.4) | 20 (15.0)b |
| Third | 109,983 (21.0) | 9019 (21.2) | 94 (19.6) | 34 (25.6)b |
| Fourth | 109,745 (21.0) | 9552 (22.5) | 92 (19.2) | 20 (15.0)b |
| Fifth (highest) | 82,148 (15.7) | 8313 (19.5)b | 77 (16.1) | 28 (21.1)b |
| Rural residencec | 37,096 (7.1) | 3025 (7.1) | 37 (7.7) | 11 (8.3) |
| Obstetric and medical history, N (%) | ||||
| Nulliparous | 215, 525 (41.3) | 15,223 (35.8)b | 140 (29.2)b | 52 (39.1) |
| Multiple gestation | 10,773 (2.1) | 1103 (2.6) | 12 (2.5) | 9 (6.8)b |
| Diabetesd | 35,435 (6.8) | 2718 (6.4) | 53 (11.1)b | 30 (22.6)b |
| Hypertensiond | 36,687 (7.0) | 4171 (9.8) | 107 (22.3)b | 49 (36.8)b |
| Health care utilization | ||||
| Family physician visits in year before conception, median (25th, 75th percentile) | 4 (2, 8) | 4 (2, 7) | 4 (2, 8) | 4 (2, 8) |
| One or more nephrologist visits from 2 years before conception up to delivery, N (%) | 10,197 (2.0) | 1302 (3.1) | 136 (28.4)b | 95 (71.4)b |
In accordance with ICES privacy policies, cell sizes <6 cannot be reported.
The N for each eGFR category provides the number of pregnancies. The number of unique mothers is calculated within each eGFR category. It is possible for a mother to have different eGFR categories for each of her pregnancies; therefore, the sum of percentages for unique mothers across eGFR categories will >100%.
Standardized difference ≥10% compared with preserved renal function (eGFR ≥90 ml/min per 1.73 m2) category. Note that the standardized difference has not been adjusted for correlation of pregnancies in women and is intended to be used as a descriptive statistic rather than making inferences about the characteristics.
Rural location was defined as a population <10,000 individuals. Patients with missing location (<0.5%) were coded as urban.
Comorbidities in the 5 years preceding the index date were considered.