Table 1. Characteristics of the Study Population by In-utero Exposure to Magnetic Fields (MF).
| 90th Percentile MF | |||||
|---|---|---|---|---|---|
| ≤1.5 mG | 1.5–2.5 mG | >2.5 mG | Chi-square | ||
| Characteristics | Category | N = 239 (%) | N = 218 (%) | N = 276 (%) | p-value |
| Maternal factors | |||||
| Age at delivery | < 25 | 37 (15.5) | 26 (11.9) | 40 (14.5) | |
| 25–30 | 64 (26.8) | 73 (33.5) | 73 (26.5) | ||
| 30–35 | 77 (32.2) | 73 (33.5) | 101 (36.6) | ||
| 35+ | 61 (25.5) | 46 (21.1) | 62 (22.5) | 0.49 | |
| Education | <College | 133 (55.7) | 116 (53.5) | 157 (56.9) | |
| College degree | 70 (29.3) | 63 (29.0) | 76 (27.5) | ||
| Graduate school | 36 (15.1) | 38 (17.5) | 43 (15.6) | 0.93 | |
| Race | White | 78 (32.6) | 92 (42.4) | 110 (39.9) | |
| Black | 18 (7.5) | 12 (5.5) | 19 (6.9) | ||
| Hispanic | 54 (22.6) | 44 (20.2) | 58 (21.0) | ||
| Asian/Pacific Islander | 73 (30.5) | 60 (27.5) | 77 (27.9) | ||
| Other/Unknown | 16 (6.7) | 10 (4.6) | 12 (4.4) | 0.55 | |
| Income | <$30,000 | 52 (22.9) | 33 (16.1) | 48 (18.2) | |
| $30,000–60,000 | 79 (34.8) | 88 (42.9) | 131 (49.6) | ||
| ≥$60,000 | 96 (42.3) | 84 (41.0) | 85 (32.2) | 0.01 | |
| Marital Status | Single | 13 (5.4) | 8 (3.7) | 17 (6.2) | |
| Married | 200 (83.7) | 181 (83.0) | 222 (80.4) | ||
| Live with partner | 19 ( 8.0) | 25 (11.5) | 28 (10.1) | ||
| Other | 7 (2.9) | 4 (1.8) | 9 (3.3) | 0.66 | |
| Pre-pregnancy BMI | ≤ 25 | 164 (68.6) | 154 (70.6) | 195 (70.7) | |
| >25 | 75 (31.4) | 64 (29.4) | 81 (29.4) | 0.85 | |
| Pre-existing or gestational diabetes | No | 210 (90.5) | 202 (95.7) | 245 (92.1) | |
| Yes | 22 (9.5) | 9 (4.3) | 21 (7.9) | 0.10 | |
| Number of previous live births | 0 | 103 (43.1) | 104 (47.7) | 135 (48.9) | |
| 1 | 93 (38.9) | 78 (35.8) | 95 (34.4) | ||
| 2+ | 43 (18.0) | 36 (16.5) | 46 (16.7) | 0.75 | |
| Index pregnancy factors | |||||
| Maternal smoking during pregnancy | No | 217 (90.8) | 200 (91.7) | 249 (90.2) | |
| Yes | 22 (9.2) | 18 (8.3) | 27 (9.8) | 0.84 | |
| Preterm Delivery | No | 219 (92.4) | 206 (94.9) | 252 (92.3) | |
| Yes | 18 (7.6) | 11 (5.1) | 21 (7.7) | 0.45 | |
| Child sex | Male | 122 (51.1) | 124 (56.9) | 134 (48.6) | |
| Female | 117 (49.0) | 94 (43.1) | 142 (51.5) | 0.18 | |
| Childhood characteristics | |||||
| Breastfed | No | 16 (6.7) | 23 (10.6) | 26 (9.4) | |
| Yes | 223 (93.3) | 194 (89.4) | 250 (90.6) | 0.32 | |
| Eat at least 5 servings of fruits and vegetables | No | 51 (40.2) | 23 (20.9) | 56 (35.7) | |
| per dayb | Yes | 76 (59.8) | 87 (79.1) | 101 (64.3) | 0.005 |
| TV, computer, video game time limited to 1 hour | No | 24 (20.3) | 15 (14.6) | 32 (22.1) | |
| per dayb | Yes | 94 (79.7) | 88 (85.4) | 113 (77.9) | 0.32 |
| Exercise at least 30–60 minutes per dayb | No | 14 (12.2) | 9 (8.9) | 13 (9.0) | |
| Yes | 101 (87.8) | 92 (91.1) | 131 (91.0) | 0.64 | |
| Play any sportsb | No | 22 (19.5) | 14 (14.4) | 29 (20.9) | |
| Yes | 91 (80.5) | 83 (85.6) | 110 (79.1) | 0.44 | |
| Outcome measurements | |||||
| Number of weight measurements in analysis (mean ± sd) | 11.3 ± 5.6 | 10.9 ± 6.0 | 11.3 ± 6.0 | 0.74a | |
| Other factors | |||||
| Child still a Kaiser member at age 11 | No | 105 (43.9) | 98 (45.0) | 120 (43.5) | |
| Yes | 134 (56.1) | 120 (55.1) | 156 (56.5) | 0.95 | |
aP-value from ANOVA F test.
bChildhood characteristics from sub-sample of children whose data was collected at well-child visits.