TABLE 3.
Improved Balance of Measured Covariates Between High-level NICUs and Other Delivery Hospitals After Use of Instrument and Matching, Pennsylvania, California, and Missouri, 1995–2005
| Pennsylvania | California | Missouri | |||||||
|---|---|---|---|---|---|---|---|---|---|
| High-level NICU | Other Delivery Hospital | Δ/SDa | High-level NICU | Other Delivery Hospital | Δ/SDa | High-level NICU | Other Delivery Hospital | Δ/SDa | |
| Birth weight, g | 2598 | 2597 | 0.00 | 2849 | 2849 | 0.00 | 2818 | 2817 | 0.00 |
| Gestational age, wk | 35.2 | 35.2 | 0.00 | 35.2 | 35.2 | 0.00 | 35.2 | 35.2 | 0.00 |
| Race | |||||||||
| White | 85.0% | 85.9% | −0.02 | 68.4% | 71.9% | −0.07 | 91.6% | 91.7% | 0.00 |
| Black | 5.1% | 4.7% | 0.01 | 5.9% | 5.8% | 0.01 | 7.3% | 7.3% | 0.00 |
| Asian | 1.1% | 0.4% | 0.06 | 8.0% | 6.8% | 0.04 | 0.6% | 0.5% | 0.01 |
| Other | 2.3% | 1.3% | 0.05 | 16.5% | 13.9% | 0.06 | 0.4% | 0.4% | 0.00 |
| Insurance status | |||||||||
| FFS | 23.9% | 25.1% | −0.03 | 3.3% | 5.4% | −0.09 | 27.8% | 25.6% | 0.05 |
| HMO | 37.0% | 30.9% | 0.13 | 45.7% | 44.2% | 0.03 | 21.1% | 19.7% | 0.03 |
| Public | 28.7% | 33.4% | −0.10 | 47.2% | 45.6% | 0.03 | 45.5% | 49.1% | −0.07 |
| Other | 9.1% | 9.0% | 0.00 | 0.9% | 1.5% | −0.06 | 3.3% | 3.6% | −0.01 |
| Uninsured | 1.0% | 1.2% | −0.01 | 3.0% | 3.3% | −0.02 | 2.3% | 2.0% | 0.01 |
| Singleton birth | 84.4% | 83.9% | 0.01 | 89.7% | 88.9% | 0.03 | 90.6% | 90.1% | 0.02 |
| SGA | 16.0% | 16.4% | −0.01 | 10.7% | 10.9% | −0.01 | 11.9% | 11.7% | 0.01 |
| Maternal comorbid conditions and complications of pregnancy | |||||||||
| Comorbid conditions | |||||||||
| Chronic HTN | 1.1% | 1.2% | 0.00 | 0.9% | 1.0% | −0.01 | 1.0% | 1.0% | 0.00 |
| Gestational diabetes | 4.7% | 4.7% | 0.00 | 5.2% | 5.3% | 0.00 | 3.8% | 3.4% | 0.02 |
| Diabetes mellitus | 1.4% | 1.8% | −0.03 | 1.0% | 1.1% | 0.00 | 1.0% | 1.1% | −0.01 |
| Renal disease | 0.2% | 0.3% | −0.01 | 0.1% | 0.2% | −0.01 | 0.2% | 0.2% | −0.01 |
| Congenital heart disease | 0.1% | 0.1% | 0.00 | 0.0% | 0.1% | −0.01 | 0.1% | 0.0% | 0.01 |
| Complications of pregnancy | |||||||||
| Preterm labor | 45.2% | 45.2% | 0.00 | 28.7% | 28.4% | 0.01 | 30.0% | 29.9% | 0.00 |
| PIH | 9.7% | 10.4% | −0.03 | 6.6% | 7.6% | −0.04 | 8.0% | 8.3% | −0.01 |
| PROM | 18.3% | 17.7% | 0.02 | 10.2% | 11.4% | −0.04 | 11.5% | 11.6% | 0.00 |
| Oligohydramnios | 3.3% | 3.1% | 0.01 | 3.0% | 2.9% | 0.00 | 3.8% | 3.5% | 0.01 |
| Disorders of placentation | 4.2% | 5.0% | −0.03 | 3.7% | 4.2% | −0.03 | 3.2% | 3.7% | −0.02 |
FFS, fee for service; HMO, health maintenance organization; SGA, small for gestational age; HTN, hypertension; PIH, pregnancy-induced hypertension; PROM, premature rupture of membranes.
a
Δ/SD is the standardized difference between the high-level NICU and other delivery hospital groups for a specific variable, defined as (difference in means between 2 groups of patients) ÷ (SD of entire cohort). A value <0.20 is considered adequate balance between groups.