TABLE 1.
Basic characteristics of the study populations
| EARLI (n = 127) |
NHSII (n = 713) | |
|---|---|---|
| n (%) | ||
| Child’s sex | ||
| M | 69 (54.3) | 414 (58.1) |
| F | 58 (45.7) | 299 (41.9) |
| Maternal ethnicity | ||
| Hispanic/Latino | 24 (18.9) | 13 (1.8) |
| Not Hispanic/Latino | 103 (81.1) | 700 (98.2) |
| Maternal race | ||
| White | 87 (68.5) | 694 (97.3) |
| Black/African American | 7 (5.5) | 1 (0.1) |
| Native American or Native Alaskan | 2 (1.6) | 0 |
| Asian | 13 (10.2) | 9 (1.3) |
| Multiple/other race | 13 (10.2) | 7 (1.0) |
| Missing | 5 (3.9) | 2 (0.3) |
| Household income1 | ||
| Low | 25 (19.7) | 26 (3.7) |
| Medium | 51 (40.2) | 308 (43.2) |
| High | 51 (40.2) | 244 (34.2) |
| Missing | 0 (0) | 135 (18.9) |
| Prenatal smoking | ||
| Active | 4 (3.2) | 51 (7.2) |
| Passive | 2 (1.6) | - |
| None | 98 (77.2) | 662 (92.9) |
| Missing | 23 (18.1) | 0 (0) |
| Birth weight | ||
| ≤2500 g | 5 (3.9) | 7 (1.0) |
| >2500 g | 121 (95.3) | 433 (60.7) |
| Missing | 1 (0.8) | 273 (38.3) |
| Ever breastfeed | ||
| Yes | 80 (63.0) | 678 (95.1) |
| No | 33 (26.0) | 34 (4.8) |
| Missing | 14 (11.0) | 1 (0.1) |
| Prenatal vitamin use2 | ||
| Yes | 73 (57.5) | 524 (73.5) |
| No | 53 (41.7) | 189 (26.5) |
| Missing | 1 (0.8) | 0 (0) |
| ASD diagnosis | ||
| Yes | 29 (22.8) | 102 (14.3)3 |
| No | 96 (75.6) | 611 (85.7) |
| Missing | 2 (1.6) | 0 (0) |
| Mean (SD) | ||
|---|---|---|
| Maternal age, y | 33.9 (4.4) | 34.2 (4.2) |
| Parity4 | 1.7 (0.9) | 1.3 (1.2) |
| Pre-pregnancy BMI, kg/m2 | 28.2 (7.4) | 23.4 (4.2) |
| Physical activity, METs/wk | 5.6 (9.4) | 20.3 (26.2) |
| Total calorie intake, kcal | 1833.8 (793.4) | 1945.6 (549.3) |
| Total SRS raw score | 36.0 (26.4) | 27.9 (33.6) |
ASD, autism spectrum disorder; EARLI, Early Autism Risks Longitudinal Investigation; MET, metabolic equivalent; NHSII, Nurses’ Health Study II; SRS, Social Responsiveness Scale.
Low-income category defined as <$50,000 in EARLI and <$40,000 in NHSII; medium category as $50,000–$100,000 in EARLI and $40,000–$100,000 in NHSII; high as >$100,000 in both studies.
For the EARLI sample, this is defined as use initiated in the first month of pregnancy; for the NHSII sample, this was prenatal vitamin use during pregnancy in general; the use of prenatal vitamins overall was high in both cohorts.
Note that due to the case-control design from which NHSII data for this analysis are drawn, the prevalence of ASD is skewed higher than the general population. The overall prevalence of ASD in the NHSII is approximately 2%.
Parity value does not include the study child in EARLI; by design, all children in EARLI were 2nd or later birth order.