Perinatal care at the threshold of viability--from principles to practice.

The threatened birth of an extremely-low-birth-weight (ELBW) and gestational age infant presents complex medical, social and ethical issues for the family and the health professionals. Improved survival may be accompanied by increased risks of chronic medical problems and neurodevelopmental disabilities. It is difficult to define "how small is too small" and to decide "how much is too much" in providing optimal management of the mother and infant when delivery takes place at the threshold of viability. An individualised prognostic strategy appears to be the most appropriate approach. Through a process of communication and value exploration between the well-meaning parents and well-intentioned physicians, the goal is to reach a consensual decision that respects parental authority and promotes physician beneficence, with the best interests of the infant placed in the centre of the analysis.