The survival rate for extremely preterm newborns born at the threshold of viability (25 or fewer completed weeks of gestation) improved in the early 1990s, largely as the result of a greater use of assisted ventilation in the delivery room and surfactant therapy. This led WHO in 1993 to define the perinatal period as commencing at 22 completed weeks of gestation. Infants born at 22-28 weeks gestation have been termed as having "threshold viability", though in developed countries this term is more often used in reference to infants of < 26 weeks. However, this improvement in survival has not been associated with an equal improvement in morbidity The increasing potential risk of residual disability or early death associated with decreasing gestational age raises serious medical, social and ethical problems in respect to appropriate management. These include whether elective delivery for fetal indication is appropriate or whether intensive care should be provided following delivery.