Executive summary of the workshop on the border of viability.

One of the most complex areas in perinatal-neonatal medicine remains the care of the mother delivering a newborn infant at the border of viability, referred to as "periviable" gestation. To address the knowledge gaps that preclude optimal, evidence-based care in this critical field of perinatal medicine, the National Institute of Child Health and Human Development organized a workshop in March 2004. This article provides a summary of the discussions, focusing on major knowledge gaps and prioritized suggestions for studies in this area.