It is important to understand that sexual intercourse may affect the diagnosis of preterm labor with use of fetal fibronectin levels because of the existence of high levels in semen, which could create false-positive results. Any positive fetal fibronectin test results should be repeated 96 hours after the episode of intercourse. This test is not yet in general clinic use but is used in those at risk of preterm labor, such as women with a positive history, women with cervical change or women with multifetal gestation. Early dilatation, although something to monitor, is not always an indication of preterm labor. The external opening to the cervix may open slightly, especially in women who have had previous births.
Preterm labor is different from incompetent cervix.
A cervix that suddenly dilates with no uterine contractions is more characteristic of incompetence. Such a condition can be managed through the use of a suture placed through and around the cervix to close it. One of the biggest risk factors for preterm labor is prior occurrence. If you've had a previous preterm birth, your risk is high that you will have another. Watch this report about showing affection to boys.