Clinical characteristics of VLBW cohort categorized according to PPROM.

p-values are derived from Fisher´s exact test or Mann-Whitney-U-test if indicated (*)Clinical characteristics of VLBW cohort categorized according to PPROM.若标注有(*)，则P值取自费希尔精确检验（Fisher´s exact test）或曼-惠特尼U检验（Mann-Whitney-U-test）。按早产胎膜早破（preterm premature rupture of membranes, PPROM）分组的极低出生体重（very low birth weight, VLBW）队列临床特征。