Maternal transport and the perinatal denominator.

In conjunction with an active outreach program, a rural perinatal region of 18,000 deliveries was analyzed. All pregnancies which resulted in the delivery of live-born infants weighing 1,000 to 1,500 gm were reviewed for maternal/fetal risk and eventual neonatal outcome. Analysis included all mothers and infants cared for at regional hospitals as well as those transferred to any tertiary care center in the state system. Thus, an entire "perinatal denominator" for this group of patients at very high risk was identified. Maternal/fetal risk scoring was highest for the group of mothers transferred to the tertiary center prior to delivery. In spite of this increased risk, infant mortality was significantly decreased by delivery at the tertiary care center. It is recommended that other groups of high-risk conditions be evaluated in regional systems only after the entire perinatal denominator has been identified.