Table 1. Descriptive data for variables included in the analyses.
| Total sample | ||
| n = 34 (17 MZ twin pairs, 47% female) | ||
| Mean (SD) | Range | |
| Individual-level description | ||
| Age (years) | 37.8 (11.2) | 22–56 |
| Weeks of gestation | 36.9 (2.4) | 30–39 |
| BW (kilograms) | 2.4 (0.5) | 1.4–3.4 |
| WM score | 110.4 (13.4) | 89–142 |
| Methylation fraction* | 43.4 (11.9)% | 20.7–60.8% |
| MZ twin intrapair differences | ||
| BW differences (kilograms) | 0.3 (0.3) | 0–1 |
| WM score differences | 8.8 (6.1) | 0–17 |
| Methylation fraction* differences | 4.4 (6.7)% | 0.3–28.8% |
MZ = monozygotic; SD = standard deviation; BW = birth weight; WM = working memory; IQ = intellectual quotient; *: average methylation fraction of cg07075026 and cg20966754 (IGF2BP1) (see Materials and methods: b. CpG region selection).