For reasons that are not clear, increasing numbers of high-risk infants are being delivered in facilities other than subspecialty or high-level neonatal intensive care units (NICUs), despite recognition that outcomes are better than for infants born in hospitals that have no NICU or only a mid-level (specialty) facility. It appears that a trend for high-risk births (less than 1500 g or earlier than 32 weeks’ gestation) to take place in subspecialty facilities, evident in the 1970s and early 1980s, slowed or even reversed in the 1990s. Proliferation of mid-level NICUs may be partly responsible. The investigators used data from birth and death certificates and hospital discharge records for singleton low birth weight (LBW) infants weighing 500–2499 g who were born in California in the years 1993–2000 in order to determine whether and how adding a new mid-level NICU influenced birth sites.
The likelihood that an infant weighing 500 to 1499 g would be born in a mid-level NICU increased by 17 percentage points when a new unit opened nearby. More than three-fourths of this change (15 percentage points) was ascribed to a reduced probability of birth at a hospital having a high-level unit. The remaining 2 percentage points reflected a lower proportion of newborn infants delivered at hospitals having a low-level center. Patterns were similar for infants weighing 1500 to 2499 g at birth. Logistic regression analyses showed that the findings could not be attributed to differences in the baseline characteristics of different areas or their populations. The proportion of very low birth weight infants born in mid-level units increased in areas with a new NICU relative to rates of birth in both low- and high-level hospitals.
In this study, conducted in California, introduction of a new mid-level NICU was associated with a significant shift of births to the new unit from both high- and low-level hospitals. The larger part of this change appeared to represent a shift from births at high-level units. These findings suggest that the continued proliferation of mid-level NICUs should be carefully considered.