Numerous descriptive studies have highlighted the aetiological heterogeneity of preterm birth, emphasizing its multifactorial origins. A classical epidemiological review acertained well established risk factors: previous low birth-weight or preterm delivery, repeated second trimester abortion, uterine and cervical anomalies, in-vitro fertilization, muliple pregnancy, maternal medical  complications, gestasional bleeding, abnormal placentation, urogenital infection, Afro-American ethnic origin,  low socio-economic status, social  isolation, smoking and low body mass index (BMI) before conception. Other factors such as maternal age, parity, infertility, heredity, drug abuse, strenuous physical work-load, sexual activities, psychosocial stress or stressful life events, inadequate or no prenatal care, maternal weigh gain are still debate