Delivery before 37 weeks of pregnancy, known as preterm delivery, occurs in 10 percent of pregnancies, the American Congress of Obstetricians and Gynecologists states. Preterm delivery has many risks for the newborn---preterm babies can have physical and mental long term effects, from cerebral palsy to learning disabilities and lung and intestinal problems. Eight or more contractions an hour over the course of an hour or more can indicate the start of preterm labor. Other tests are done to assess whether preterm labor is really commencing.
Fetal Fibronectin
Fetal fibronectin, or fFN, is a protein that attaches the amniotic sac to the uterine wall. FFN is usually not detected in vaginal secretion between week 24 and 34 of pregnancy, so its presence in vaginal secretions may indicate that this "glue" is disintegrating early, the March of Dimes reports. A swab of vaginal or cervical secretions is tested and test results take 24 hours to obtain. FFN is not a definitive test of preterm labor, but less than 5 percent of women with a negative test result deliver within the subsequent two weeks, according to the March of Dimes. A positive test doesn't mean delivery will definitely occur within two weeks, but may be an indication that more aggressive treatment, including corticosteroid administration to mature the fetal lungs, should be considered.
Transvaginal Ultrasound
Transvaginal ultrasound, done via a probe inserted into the vagina, can measure the length and thickness of the cervix. True preterm labor usually begins with the shortening and thinning of the cervix, so several ultrasounds may be done to assess for any change in the cervix. A study reported by OBGYN.net conducted by lead author M.G. Crane M.D, of the Obstetrics and Gynecology Department at Memorial University in Newfoundland, Canada found that cervical length of 3 cm or less was a better indicator of preterm delivery than other tests, at least in singleton pregnancies.
External Fetal Monitoring
External fetal monitoring is done by placing a tocodynamometer, a device that registers tightening of the uterus, against the uterus. Many women have contractions throughout pregnancy, so it's important to differentiate contractions that need aggressive treatment and those that aren't causing any cervical change. A woman experiencing regular contractions prematurely should be monitored externally to assess the frequency of contractions. If labor is occurring, contractions generally become more frequent and more intense.
Vaginal Examination
Once labor begins, the cervix begins to thin. It may also begin to open, or dilate. An internal exam, done through the vagina to manually check the cervix, may be done. Exams may be done several hours apart to check for any cervical change that would indicate the start of true preterm labor. Evidence of cervical change is necessary for the diagnosis of preterm labor, the March of Dimes states.
