A method of determining risk of preterm labor in an asymptomatic pregnant woman can include: obtaining a vaginal fluid sample from an asymptomatic pregnant woman； contacting the vaginal fluid sample with a PAMG-1 antibody that binds with PAMG-1； detecting whether the PAMG-1 antibody binds with PAMG-1 in the vaginal fluid sample to form a PAMG-1-antibody complex； and providing the determined risk to the pregnant woman. When the PAMG-1-antibody complex forms, the asymptomatic pregnant woman is determined to be susceptible to preterm labor because PAMG-1 is detected in the vaginal sample. When the PAMG-1-antibody complex does not form, the asymptomatic pregnant woman is determined to be not susceptible to preterm labor because the PAMG-1 is not detected in the vaginal sample.
