Table 3.
Characteristics of SELF Participants at Time of Enrollment
| Characteristic | n (%) (N = 1696) |
|---|---|
| Participant age at ultrasound (years) | |
| 23–25 | 378 (22) |
| 26–28 | 424 (25) |
| 29–31 | 459 (27) |
| 32–35 | 435 (26) |
| Education | |
| ≤High school or GED | 370 (22) |
| Some college or associate/technical degree | 850 (50) |
| Bachelor's, master's, or doctoral degree | 475 (28) |
| Missing | 1 |
| Total annual household income (USD) | |
| <20,000 | 768 (46) |
| 20,000–50,000 | 629 (37) |
| >50,000 | 287 (17) |
| Missing | 12 |
| Age at menarche (years) | |
| ≤10 | 310 (18) |
| 11 | 334 (20) |
| 12 | 459 (27) |
| 13 | 287 (17) |
| ≥14 | 306 (18) |
| Gravidity | |
| Ever pregnant | 1244 (73) |
| Never pregnant | 452 (27) |
| Parity (number of births) | |
| 0 | 663 (39) |
| 1 | 433 (26) |
| 2 | 313 (18) |
| ≥3 | 287 (17) |
| Number of miscarriages (among gravid) | |
| 0 | 926 (75) |
| 1 | 240 (19) |
| ≥2 | 72 (6) |
| Missinga | 6 |
| Number of induced abortions (among gravid) | |
| 0 | 570 (46) |
| 1 | 345 (28) |
| ≥2 | 324 (26) |
| Missingb | 5 |
| History of hormonal contraceptionc | |
| None | 237 (14) |
| Oral contraceptives | 1200 (71) |
| Depo-Provera | 722 (43) |
| Hormone patch | 304 (18) |
| Vaginal ring | 227 (13) |
| Mirena IUD | 191 (11) |
| Hormone implant | 42 (2) |
| Body mass index (kg/m2) | |
| <25.0 | 336 (20) |
| 25.0 to <30.0 | 350 (21) |
| 30.0 to <35.0 | 329 (19) |
| ≥35.0 | 681 (40) |
| Prior diagnosis of: | |
| Hypertension | |
| Yes | 168 (10) |
| No | 1510 (90) |
| Missing | 18 |
| Diabetes | |
| Yes | 57 (3) |
| No | 1627 (97) |
| Missing | 12 |
| Asthma | |
| Yes | 331 (20) |
| No | 1348 (80) |
| Missing | 17 |
| Chlamydia | |
| Yes | 632 (37) |
| No | 1062 (63) |
| Missing | 2 |
| Gonorrhea | |
| Yes | 324 (19) |
| No | 1371 (81) |
| Missing | 1 |
| Smoking status | |
| Never | 1247 (74) |
| Past | 125 (7) |
| Current | 324 (19) |
| Alcohol use (at time when drinking the most)d | |
| Low/never | 450 (27) |
| Moderate | 554 (33) |
| Heavy | 692 (41) |
| Early life exposures | |
| Maternal smoking (in utero exposure) | |
| No | 1252 (74) |
| Yes | 444 (26) |
| Born a week or more before due datee | |
| No | 1145 (76) |
| Yes, born 1–2 weeks early | 212 (14) |
| Yes, born ≥3 weeks early | 148 (10) |
| Missing | 191 |
| Fed soy formula as infante | |
| No | 1355 (87) |
| Yes | 198 (13) |
| Missing | 143 |
| Breastfed as infante | |
| No | 1076 (68) |
| Yes | 496 (32) |
| Missing | 124 |
| Frequency of childhood hair treatment with chemical products, including hair straighteners, around age 10 years | |
| Rarely/never | 939 (55) |
| Once a year | 183 (11) |
| 2 to 4 times a year | 331 (20) |
| 5 to 9 times a year | 196 (12) |
| 10 or more times a year | 45 (3) |
| Missing | 2 |
| Uterine fibroids at baseline ultrasoundf | |
| No | 1318 (78) |
| Yes | 378 (22) |
| Number of fibroids (among those with fibroids) | |
| 1 | 240 (63) |
| 2 | 56 (15) |
| ≥3 | 82 (22) |
| Size of largest fibroidg (cm) (among those with fibroids) | |
| <2 | 234 (62) |
| 2–3.9 | 93 (25) |
| ≥4 | 51 (13) |
| Fibroid type (among those with fibroids) | |
| Any submucosal | 34 (9) |
| Any intramural | 313 (83) |
| Any subserosal | 104 (28) |
| Fibroid location (among those with fibroids) | |
| Any fundal | 174 (46) |
| Any corpus | 273 (72) |
| Any lower uterine segment | 30 (8) |
Missing includes 2 women with one or two miscarriages and 2 women with up to two miscarriages with the possibility of none.
Missing includes 2 women with one or two abortions and 3 women with up to two abortions with the possibility of none.
Women often had used more than one form of hormonal birth control.
Low/moderate drinkers never drank more than 10 drinks in a year. Heavy drinkers usually drank six or more drinks on days when they drank or drank four or more drinks per sitting at least two to three times a month. Moderate drinkers were everyone else.
Data from the Early Life Questionnaire has more missing data because it involved consultation with mother or others who knew of participant's early life and had to be mailed back to study center (n = 74 not yet returned). Also, 24 participants were not given a form because they had no one to ask.
Includes six questionable fibroids that could not be seen in all three dimensions. Each was the single fibroid detected.
Based on maximum diameter measured.
GED, General Educational Development test (high school equivalency); IUD, intrauterine device.