Background: We evaluated the process of regionalization of high risk perinatal care by comparing data on hospital of birth of very low birthweight infants between 1983 and 1993.

Subjects: Infants of less than 32 weeks gestation and/or less than 1500 gram birth weight.

Methods: The 1993 National Obsteries Registration (LVR) data on hospital of birth were analyzed for the level of care. The 1993 National Neonatology Registration (LNR) data were analyzed for hospital of birth and in-hospital mortality. A comparison was made with the data from 1983, which were available from the Project On Preterm and Small for gestational age infants (POPS).

Results: It could be calculated from the LVR data that the percentage of infants below 32 weeks of gestation delivered in level III hospitals increased from 34% in 1983 to 68% in 1993 and the percentage of those born in level I hospitals decreased from 50% to 22%. In 1983, 1338 infants < 32 wks and/or < 1500 g were born. Of those, 481 (36%) were inborn in a perinatal center. According to the 1993 LNR data 1097 (68%) of 1610 similar infants were inborn in perinatal centers In-hospital mortality in 1993 was 16.0%, compared to 25.4% in 1983. Total perinatal mortality in the Netherlands was 9.1 per 1000 in 1993 (stillbirths from 24 weeks included), and 10.1 per 1000 in 1983 (stillbirths from 28 weeks included).

Conclusion: Concentration of high risk perinatal care in regional perinatal centers substantially increased: most very low birthweight infants now are inborn. mortality decreased further.