\-Cervical changes and regular contractions occurring between 20-37 weeks.
\-Morbidity/Mortality- survival rate increases as gestational age increases
\-Risk Factors-
\--History of abruption, uterine over distension, cervical incompetence, bacterial infections, multiple gestations, HTN, DM, low pregnancy weight, late or no prenatal care, smoking ,drugs, alcohol, trauma, stress, etc.