We conducted a survey of 1,064 out-of-hospital Kentucky births during 1981 to 1983 in order to classify each by planning status (planned or unplanned to occur out of hospital) and attendant. Among the 809 births for which we obtained information, 575 (71.1%) were planned. We examined birth outcome by low birth weight (LBW) and neonatal mortality (NM). Compared with planned births, unplanned births were associated with increased risk of LBW (odds ratio = 6.6; 95% confidence limits [CL], 3.9 to 11.2, adjusted for maternal age). Furthermore, after adjusting for maternal age and parity, LBW births occurred at less than expected frequency among planned births (observed to expected [O:E] ratio = 0.48; 95% CL, 0.29 to 0.73), but at greater than expected frequency among unplanned births (O:E ratio = 2.9; 95% CL, 2.2 to 3.8). A similar, but nonsignificant, trend was seen for NM and NM was much greater in the unplanned group (72.7 per 1,000 live births) than in the planned group (3.5 per 1,000).