“…Numerous factors have been associated with an increased risk of PTB and its recurrence. These include history of preterm birth, low maternal body mass index, pre-eclampsia, placenta previa, and short cervical length [12,13]. Furthermore, genital infection, multiple gestation, short interpregnancy interval, uterine anomalies, smoking, black race, raised fetal fibronection concentration, psychological stress, stressful working condition, poor living condition, low level of education and maternal unemployment status have aso been associated with an increased risk of PTB and its recurrence [14][15][16].…”