Table 2.

Methylation percentages of each of 20 CpG sites within the SLC6A4 promoter region for low-pain exposed and high-pain exposed very preterm infants at birth and at NICU discharge.

SLC6A4 CpG sites	Methylation at birth				Methylation at NICU discharge
	LPE VPT infants		HPE VPT infants		LPE VPT infants		HPE VPT infants
	Mean	SD	Mean	SD	Mean	SD	Mean	SD
CpG site1	1.09	0.71	1.15	0.95	1.17	0.85	1.00	0.72
CpG site2	0.86	0.92	0.48	0.52	0.79	0.64	0.94	0.51
CpG site3	1.54	1.06	1.16	0.82	1.24	0.92	1.30	0.64
CpG site4	1.24	0.78	1.36	0.83	1.52	0.98	1.53	0.90
CpG site5	1.06	0.71	0.69	0.49	1.05	1.10	1.39	0.98
CpG site6	0.86	0.63	0.59	0.70	0.49	0.42	0.80	0.45
CpG site7	0.52	0.42	0.29	0.33	0.60	0.53	0.54	0.47
CpG site8	0.73	0.67	0.58	0.64	0.43	0.40	0.54	0.44
CpG site9	1.80	1.10	1.68	1.17	2.25	2.09	1.79	1.05
CpG site10	1.26	1.19	1.13	1.33	1.48	2.10	1.16	1.05
CpG site11	0.91	0.75	0.86	1.08	1.11	2.05	0.73	0.38
CpG site12	3.17	1.38	3.14	1.31	3.44	1.61	3.48	1.07
CpG site13	0.85	0.58	0.75	0.61	0.80	0.72	0.86	0.53
CpG site14	0.91	0.74	1.06	1.27	0.86	0.92	0.80	0.69
CpG site15	0.55	0.58	0.72	0.90	0.72	0.67	0.63	0.46
CpG site16	1.20	0.81	0.79	0.62	1.11	0.82	1.13	0.64
CpG site17	1.27	0.76	1.21	1.13	1.24	1.20	1.08	0.74
CpG site18	0.94	0.95	0.87	0.81	0.99	1.03	0.75	0.59
CpG site19	0.71	0.62	0.55	0.50	0.71	0.65	0.40	0.33
CpG site20	0.33	0.44	0.26	0.37	0.38	0.71	0.28	0.41

LPE VPT, Low-pain exposed very preterm infants; HPE VPT, High-pain exposed very preterm infants.