Diagnosis

Your health care provider will review your medical history and risk factors for preterm labor and evaluate your signs and symptoms. If you're experiencing regular uterine contractions and your cervix has begun to soften, thin and open (dilate) before 37 weeks of pregnancy, you'll likely be diagnosed with preterm labor.

Tests and procedures to diagnose preterm labor include:

• Pelvic exam. Your health care provider might evaluate the firmness and tenderness of your uterus and the baby's size and position. If your water hasn't broken and there's no concern that the placenta is covering the cervix (placenta previa), he or she might also do a pelvic exam to determine whether your cervix has begun to open. Your health care provider might also check for uterine bleeding.
• Ultrasound. A transvaginal ultrasound might be used to measure the length of your cervix. An ultrasound might also be done to check for problems with the baby or placenta, confirm the baby's position, assess the volume of amniotic fluid, and estimate the baby's weight.
• Uterine monitoring. Your health care provider might use a uterine monitor to measure the duration and spacing of your contractions.
• Lab tests. Your health care provider might take a swab of your vaginal secretions to check for the presence of certain infections and fetal fibronectin — a substance that acts like a glue between the fetal sac and the lining of the uterus and is discharged during labor. These results will be reviewed in combination with other risk factors. You'll also provide a urine sample, which will be tested for the presence of certain bacteria.