Serial Cervical Length Measurements After the 1st Episode of Threatened Preterm Labor to Improve Prediction of Spontaneous Preterm Delivery: Prospective Cohort Study

Preterm labor is the result of labor occurring prior to 36 6/7 weeks' gestation (i.e spontaneous preterm labor) leading to delivery. Preterm labor is a clinical diagnosis, defined as the appearance of regular contractions accompanied by a change in cervical dilation, effacement, or both, or initial presentation with regular contractions and cervical dilation of at least 2 cm prior to 36 6/7 weeks' gestation.

The pathogenesis of preterm labor has not yet been fully understood, but it has been hypothesized that it could be caused by early idiopathic activation of the normal process of labor or instead, that it could be the result of pathological insults (Goldenberg 2008, Hamilton 2013, Slattery 2002). In Western countries, spontaneous PTB is responsible for 75% of perinatal mortality and more than half of long-term morbidity (McCormick 1985). Although most preterm newborns survive, they have an increased risk of neuro-behavioral disability, cerebral palsy, mental and developmental retardation. Moreover, spontaneous PTB also represents an important cause of chronic broncho pneumopathies, visual and auditory abnormalities and other chronic diseases of the pediatric age including school failure.

As contractions are the most commonly recognized antecedent of preterm birth, cessation of uterine contractions has been the primary focus of therapeutic intervention to prevent the burden of prematurity.

Preterm labor is currently considered a syndrome with a multifactorial etiology, among which inflammation, uteroplacental ischemia or hemorrhage, uterine overdistension, stress and other immune-mediated processes certainly play a role (Romero 2006): these factors do not necessarily represent a direct cause, but contribute to a transition from uterine quiescence to preterm labor or preterm premature rupture of membranes (pPROM) (Goldenberg 2005).

There are many maternal and fetal conditions that have been associated with PTB, including maternal demographic characteristics (such as low socio-economic status, race), nutritional status, obstetric history (history of prior spontaneous PTB), psychological aspects, risk behaviors (such as drug and tobacco use), infections, short CL, as well as biological and genetic markers (Goldenberg 2008, Andrews 2000).