Table 3. Meta-regression coefficient between prevalence of preterm with sample size and year of publication .

Variable	Meta-regression coefficient	t	SE	P	95% CI
Sample size of study	-9.81×10 -6	1.40	7.02×10-6	0.179	- 24.5×10-6 –4.89×10-6
Year of publication	-1×10-3	-0.23	-5×10-3	0.821	-12.4×10-3 10×10-3