This invention is about a method for the prenatal diagnosis of preterm delivery, fetal infection, and fetal damage, and diagnostic reagent system and diagnostic kit for the diagnosis. The method, diagnostic reagent system, and kit are based on the finding that the level of MMP-8 in the amniotic fluid is significantly higher when the pregnant woman is at risk for preterm delivery, intrauterine infection, and fetal damage. The diagnostic reagent system and kit can be applied to the patients without, as well as with, clinical signs of preterm labor or premature rupture of fetal membranes. With the superiority in sensitivity and specificity as well as its less invasiveness compared to the conventional method of measuring fetal blood cytokine levels, this diagnostic reagent system and kit is very useful in the prenatal diagnosis of preterm delivery, fetal infection, and fetal damage.