Vaginal exam for preterm labor

If you have symptoms of preterm labor, your doctor or nurse-midwife will examine you by feeling your cervix. If your contractions continue over a period of hours, you may be examined periodically to see whether your cervix is opening (dilating) or thinning (effacing).

These exams allow your health professional to:

• Determine how much your cervix has opened (dilated) and thinned.
• Determine how far the baby has moved down the birth canal (station).
• Check for fluid leaking from your vagina using a sterile speculum. If fluid is present, it will be tested to determine whether it is amniotic fluid, which is a sign that your amniotic sac has ruptured.

Vaginal exams are done when a pregnant woman has:

• Uterine contractions that may have changed her cervix and may be preterm labor. The cervix may open and thin without strong or painful contractions.
• Unusual pelvic pressure or back pain.
• Vaginal bleeding.

Preterm labor is diagnosed when a woman who is 20 to 37 weeks pregnant has uterine contractions and her cervix has changed, as seen with a vaginal exam.

Preterm labor is not diagnosed if contractions are occurring but the cervix is not becoming thinner or more dilated.

When a vaginal exam is not done to assess for preterm labor

When the amniotic membranes rupture early (preterm premature rupture of membranes, or pPROM), sterile speculum exams are kept to a minimum, and digital exams are avoided. This is meant to reduce the risk of infecting the uterus and fetus.

When the placenta is known to be overlapping or covering the cervix (placenta previa), vaginal exams are completely avoided. Disturbing the placenta can trigger bleeding.

Complete the medical test information form (PDF)(What is a PDF document?) to help you prepare for this test.