Table 2. Descriptive statistics for the included subjects.
| Infants' characteristics | Mean | SD |
| Gestational age at birth (weeks) | 30.10 | 2.00 |
| Birth weight (grams) | 1285.00 | 277.00 |
| CRIB II score * | 5.80 | 2.70 |
| Days of ventilation | 19.20 | 17.00 |
| Number of skin-breaking procedures | 30.80 | 19.00 |
| Length of NICU stay (days) | 52.80 | 22.90 |
| Gestational age at MRI scan (weeks) | 40.80 | 0.90 |
| N | % | |
| Males | 12.00 | 44.00 |
| Singleton | 12.00 | 44.00 |
| Cesarean Section | 27.00 | 100.00 |
| Assisted ventilation | 26.00 | 96.20 |
| Small for gestational age † | 3.00 | 11.00 |
| Sepsis ‡ | 5.00 | 18.50 |
| Bronchopulmonary dysplasia [37] | 1.00 | 3.70 |
| Necrotizing enterocolitis [38] | 2.00 | 7.40 |
| Retinopathy of prematurity § | 2.00 | 7.40 |
| Maternal characteristics | Mean | SD |
| Age (years) | 35.17 | 4.62 |
| Education (years of study) | 16.59 | 2.15 |
| Socio-economic status (SES) ¶ | 51.48 | 19.16 |
| Variables of interest | Mean | SD |
| NICU-related stress | 0.00 | 1.00 |
| Δmet # | 0.07 | 1.23 |
| ATL-MPR | 1674.31 | 309.91 |
| ATL-MPL | 1758.76 | 366.96 |
| ATL-LPR | 1957.52 | 306.05 |
| ATL-LPL | 1937.60 | 321.38 |
| GMDS personal-social scale score | 94.88 | 9.60 |
Note.
* Clinical Risk Index for Babies–II [27]
† Small for gestational age is defined as birth weight inferior to the 10th centile
‡ Sepsis is defined as clinical signs of infection (including tachycardia/bradycardia, hypotension, poor perfusion, apnoea, cyanosis, tachypnea, need for ventilator, increased oxygen requirement, abnormal temperature, lethargy, hypotonia and feeding problems) associated with increased plasmatic levels of C reactive protein and a positive blood colture
§ Stage I retinopathy of prematurity, according to the International Classification [26]
¶ According to Hollingshead classification [28]
# Δmet SLC6A4 methylation at NICU discharge minus SLC6A4 methylation at birth at CpG chr17: 28562786–28562787; ATL-MPR, anterior temporal lobe–medial part right; ATL-MPL, anterior temporal lobe–medial part left; ATL-LPR, anterior temporal lobe–lateral part right; ATL-LPL, anterior temporal lobe–lateral part left; GMDS, Griffiths Mental Development Scales [24].