Table 2. Comparison of language proficiency of HRIs with different characteristics.

Factor	Group	Language development delay	χ²	P
Gender	Male	11 (8.9%)	2.427	0.119
	Female	3 (3.4%)
Gestational week of delivery	28–32	5 (27.8%)	8.987	0.011
	33–36	4 (4.7%)
	≥37	5 (4.6%)
Birth weight, Kg	<1.5	3 (27.3%)	5.093	0.024
	1.5–2.5	4 (7.0%)
	>2.5	7 (4.9%)
Disease diagnosis	Premature delivery	9 (8.7%)	7.14	0.069
	NRDS	1 (7.1%)
	Hyperbilirubinemia	0 (0%)
	Neonatal hypoxic ischemic encephalopathy	2 (20.0%)
	Aspiration pneumonia	2 (8.7%)
	PDA	0 (0%)
Feeding mode	Breastfeeding	13 (6.8%)	0.132	0.716
	Non-breastfeeding	1 (4.8%)
Maternal gestational age, weeks	≤24	2 (5.0%)	5.173	0.160
	25–30	6 (5.3%)
	31–35	6 (13.6%)
	≥36	0 (0%)
Abortion history	No	12 (6.1%)	0.295	0.587
	Yes	2 (13.3%)
Prenatal examination	Yes	13 (6.6%)	0.025	0.874
	No	1 (7.7%)
Diseases of perinatal mothers	Normal	12 (6.3%)	2.931	0.402
	PIH	2 (18.2%)
	Gestational diabetes mellitus	0 (0%)
	History of threatened abortion	0 (0%)
Maternal education	Below junior school	8 (27.6%)	17.396	0.000
	High school and technical secondary school	4 (5.0%)
	College degree or above	2 (2.0%)
Average monthly household income, CNY	<3,000	9 (9.6%)	2.545	0.280
	3,000–5,000	4 (4.8%)
	≥5,000	1 (3.0%)

HRI, high-risk infant; NRDS, neonatal respiratory distress syndrome; PDA, patent ductus arteriosus; PIH, pregnancy-induced hypertension syndrome.