Have the boundaries of the 'grey zone' of perinatal resuscitation changed for extremely preterm infants over 20 years?

Aim: To determine the boundaries of the grey zone of discretionary resuscitation over the past 20 years.

Background: As the likelihood of survival improves over time, the BW- and GA-specific boundaries of discretionary nonresuscitation should fall.

Hypothesis: Between 1988 and 2008 reductions in BW- and GA-specific mortality would drive a parallel reduction in BW and GA boundaries of discretionary resuscitation.

Methods: We determined the likelihood of resuscitation and survival to NICU discharge for all infants born <700 g or <26 gestational weeks from 1988 to 2008. In addition, for 1988, 1993, 1998, 2003 and 2008, we determined the BW and GA for the 10 smallest infants who were resuscitated, and the 10 largest infants who were not resuscitated. We excluded any infant born with congenital anomaly.

Results: Mortality fell from 80% in 1988 to 28% in 2008, and as expected, the percentage who were resuscitated rose from 63% in 1988-93 to 95% in 2004-2008. However, unexpectedly, over the 20-year study period, the smallest infants who were resuscitated despite extreme immaturity did not change (450-550 g and 23-24 weeks) and the largest infants not resuscitated did not change (600-700 g and 23-24 weeks.

Conclusion: Neither the BW nor GA boundaries of the grey zone of discretionary resuscitation have fallen over the past 20 years. Factors guiding resuscitation at the border of viability are complex and incompletely understood.