Table 2.
Characteristics of participants' mothers (maternal) and early life of participants (infant) by infant soy formula feeding exposure in the Study of Environment, Lifestyle & Fibroids (SELF), 2010-2012.
| Characteristic | All participants (n=1553) | Subset of participants with natural menses data (n=762)a | ||
|---|---|---|---|---|
|
| ||||
| Ever fed soy formula (n=198) | Never fed soy formula (n=1355) | Ever fed soy formula (n=89) | Never fed soy formula (n=673) | |
| n (%) | n (%) | n (%) | n (%) | |
| Maternal | ||||
| Age at delivery (years) | ||||
| 12-19 | 35 (18) | 312 (23) | 19 (21) | 158 (23) |
| 20-24 | 63 (32) | 439 (32) | 26 (29) | 224 (33) |
| 25-29 | 52 (26) | 362 (27) | 23 (26) | 170 (25) |
| 30-34 | 35 (18) | 174 (13) | 18 (20) | 87 (13) |
| 35-44 | 13 (7) | 68 (5) | 3 (3) | 34 (5) |
| Maternal smoking | ||||
| No | 147 (74) | 994 (73) | 63 (71) | 479 (71) |
| Yes | 51 (26) | 361 (27) | 26 (29) | 194 (29) |
| Gestational or pre-existing diabetes | ||||
| No | 181 (93) | 1274 (95) | 81 (92) | 638 (96) |
| Yes | 14 (7) | 65 (5) | 7 (8) | 30 (4) |
| Missing | 3 | 16 | 1 | 5 |
| Pregnancy-related hypertension or pre-eclampsia | ||||
| No | 155 (79) | 1175 (89) | 72 (81) | 582 (89) |
| Yes | 40 (21) | 148 (11) | 17 (19) | 73 (11) |
| Missing | 3 | 32 | 0 | 18 |
| Highest educational level of mother or primary caregiver when participant was age 10 years | ||||
| ≤HS or GED | 72 (36) | 643 (48) | 31 (35) | 340 (51) |
| Some college orAssociate/technical degree | 93 (47) | 557 (41) | 49 (55) | 267 (40) |
| Bachelor's/Master's/doctoral degree | 33 (17) | 153 (11) | 9 (10) | 65 (10) |
| Missing | 0 | 2 | 0 | 1 |
| Economic status during participant's childhood | ||||
| Poor | 2 (1) | 69 (5) | 1 (1) | 36 (5) |
| Low income | 72 (36) | 480 (35) | 34 (38) | 256 (38) |
| Middle income | 110 (56) | 702 (52) | 51 (57) | 337 (50) |
| Well off | 14 (7) | 103 (8) | 3 (3) | 44 (7) |
| Missing | 0 | 1 | 0 | 0 |
| Infant | ||||
| Birth weight (g) | ||||
| <2500 | 29 (15) | 181 (13) | 10 (11) | 95 (14) |
| 2500 to <3500 | 113 (57) | 853 (63) | 51 (57) | 429 (64) |
| ≥3500 | 55 (28) | 311 (23) | 28 (31) | 146 (22) |
| Missing | 1 | 10 | 0 | 3 |
| Born a week or more before due date | ||||
| No | 140 (72) | 984 (75) | 69 (78) | 484 (75) |
| Yes | 54 (28) | 325 (25) | 19 (22) | 165 (25) |
| Yes, born 1-2 weeks early | 25 (13) | 186 (14) | 8 (9) | 83 (12) |
| Yes, born ≥3weeks early | 26 (13) | 121 (9) | 11 (12) | 73 (11) |
| Yes, unknown number of weeks born early | 3 (2) | 18 (1) | 0 (0) | 9 (1) |
| Missing | 4 | 46 | 1 | 24 |
| Multiple gestation | ||||
| No | 192 (97) | 1314 (97) | 86 (97) | 650 (97) |
| Yes | 6 (3) | 41 (3) | 3 (3) | 23 (3) |
| First born | ||||
| No | 111 (57) | 776 (58) | 47 (54) | 387 (58) |
| Yes | 84 (43) | 563 (42) | 40 (46) | 277 (42) |
| Missing | 3 | 16 | 2 | 9 |
| Breastfeeding duration (months) | ||||
| Never breastfed | 105 (53) | 950 (71) | 50 (56) | 470 (70) |
| Any breastfeeding | 93 (47) | 396 (29) | 39 (44) | 200 (30) |
| <1 | 18 (9) | 64 (5) | 9 (10) | 35 (5) |
| 1-3 | 34 (17) | 105 (8) | 18 (20) | 48 (7) |
| 4-6 | 21 (11) | 78 (6) | 7 (8) | 44 (7) |
| >6 | 16 (8) | 121 (9) | 5 (6) | 58 (9) |
| Duration unknown | 4 (2) | 28 (2) | 0 (0) | 15 (2) |
| Missing | 0 | 9 | 0 | 3 |
Abbreviations: HS=high school degree; GED=general equivalency diploma.
a
Subset of participants with natural menses, defined as women who reported menstrual periods in the year before the last menstrual period and study interview date and who reported not using medications that may alter menses (hormonal birth control or other medications during the year before the last menstrual period or current use of non-steroidal anti-inflammatory drugs for heavy menstrual bleeding).