Variations in pregnancy outcomes and use of obstetric procedures in two institutions with divergent philosophies of maternity care.

Pregnancy outcomes were compared between a stratified random sample of 796 women delivering a live birth at a maternity center (BMC) and a frequency matched sample of 804 women delivering a live birth at a tertiary hospital (TJUH) in 1977-1978. The relationship of use of obstetric procedures with pregnancy outcomes was investigated within and between the two samples. The neonatal morbidity rate, as measured by Hobel's neonatal risk score, was significantly higher and mean birth weights were lower at TJUH than at BMC when adjusted for institutional differences in use of obstetric procedures, medical-obstetric risk, and demographic characteristics. Conversely, the proportion of newborns with low 1-minute Apgar scores (fewer than seven) was significantly greater at BMC. The relationship of use of obstetric procedures with each outcome varied between the two institutions as well as across the three measures of pregnancy outcomes. The relationship of use of some procedures with each outcome may be explained in part by use of the procedure because of a suspected poor outcome of pregnancy, rather than an elevated risk of poor outcomes because of use of the procedure. Self-selection of some patients to BMC cannot be ruled out as a possible explanation for institutional differences.