Table 2.

Bivariate correlations^a of frequency of SSC and HF-HRV during week 1, and measures of morbidity and short-term developmental outcomes (N = 101)

Measure	1. Week 1 SSC (times per week)	2. Week 1 HF-HRV (ms2)	3. Days on vent	4. Days on oxygen	5. LOS (d)	6. PMA full PO (wk)	7. PMA at D/C (wk)
1. Week 1 SSC (times per week)	–
2. Week 1 HF-HRV (ms2)	0.23b	–
3. Days on vent	−0.38c	−0.50c	–
4. Days on oxygen	−0.35c	−0.62c	0.68c	–
5. LOS (d)	−0.34c	−0.60c	0.57c	0.78c	–
6. PMA full PO (wk)	−0.12	−0.29c	0.27c	0.45c	0.63c	–
7. PMA at D/C (wk)	−0.23b	−0.30c	0.33c	0.47c	0.71c	0.94c	–

Abbreviations: D/C, discharge; HF-HRV, high-frequency heart rate variability; LOS, length of hospital stay; PMA, postmenstrual age; PO, by mouth; SSC, skin-to-skin contact.

^aBivariate correlations were done using Spearman’s correlation coefficients.

^bp < 0.05.

^cp < 0.01.