Table 1 Characteristics of the Study Population by Daily Magnetic Field Exposure Level (Lowest or Higher Quartiles of MF 99th Percentile).

From: Exposure to Magnetic Field Non-Ionizing Radiation and the Risk of Miscarriage: A Prospective Cohort Study

Characteristic Total N (N = 913)a 99th Percentile MF Level
Lowest quartile (N = 219) Higher quartiles (N = 694)
N % N %
Maternal age
 <30 296 61 27.9% 235 33.9%
 30–34 288 71 32.4% 217 31.3%
 ≥35 329 87 39.7% 242 34.9%
Race
 White 326 91 41.7% 235 34.0%
 Black 90 16 7.3% 74 10.7%
 Hispanic 226 51 23.4% 175 25.3%
 Asian /Pacific Islander 202 44 20.2% 158 22.8%
 Other 66 16 7.3% 50 7.2%
Education
 <High school 42 5 2.3% 37 5.4%
 High school or GED 142 32 14.7% 110 15.9%
 Trade/Technical school 46 5 2.3% 41 5.9%
 College degree 495 128 58.7% 367 53.1%
 Graduate school 184 48 22.0% 136 19.7%
Marital Status
 Single 72 12 5.5% 60 8.7%
 Partnered 147 31 14.2% 116 16.8%
 Married 690 175 80.3% 515 74.5%
Worked in last year
 No 183 47 21.6% 136 19.7%
 Yes 727 171 78.4% 556 80.3%
Smoked since LMP
 No 807 196 91.2% 611 89.3%
 Yes 92 19 8.8% 73 10.7%
Coffee intake since LMP
 0 cup/day 637 142 64.8% 495 71.3%
 0–1 cup/day 201 52 23.7% 149 21.5%
 >1 cups/day 75 25 11.4% 50 7.2%
Alcohol use since LMP
 No 514 127 58.3% 387 55.8%
 Yes 397 91 41.7% 306 44.2%
Number of previous pregnancies
 0 94 21 9.6% 73 10.5%
 1 103 18 8.2% 85 12.2%
 2 140 36 16.4% 104 15.0%
 ≥3 576 144 65.8% 432 62.2%
Number of previous miscarriages
 0 276 60 27.4% 216 31.1%
 1 79 21 9.6% 58 8.4%
 2 403 101 46.1% 302 43.5%
 ≥3 155 37 16.9% 118 17.0%
History of subfertility
 No 633 147 67.1% 486 70.0%
 Yes 280 72 32.9% 208 30.0%
Vaginal bleeding since LMP
 No 670 165 75.7% 505 72.9%
 Yes 241 53 24.3% 188 27.1%
Urinary tract infection since LMP
 No 860 211 96.8% 649 93.9%
 Yes 49 7 3.2% 42 6.1%
Fever since LMP
 No 851 198 92.1% 653 94.8%
 Yes 53 17 7.9% 36 5.2%
Carry loads (>10 pounds) since LMP
 No 416 92 42.2% 324 46.8%
 Yes 494 126 57.8% 368 53.2%
Used Jacuzzi/hot tub/steam room/sauna since LMP
 No 807 200 91.7% 607 87.7%
 Yes 103 18 8.3% 85 12.3%
Exposure to solvents or degreasers since LMP
 No 609 148 68.5% 461 67.7%
 Yes 288 68 31.5% 220 32.3%
Vitamin use since LMP
 No 91 16 7.3% 75 10.8%
 Yes 820 202 92.7% 618 89.2%
Gestational age at study entry
 0–48 days 763 173 79.0% 590 85.0%
 49–69 days 135 41 18.7% 94 13.5%
 ≥70 days 15 5 2.3% 10 1.4%
  1. Abbreviation: LMP, Last menstrual period.
  2. aThe numbers in each individual category may not sum to the total number because of missing data.