We prospectively tested the hypothesis that prevention of lateral movement of the head, using a specially designed head support apparatus, would prevent oxygen desaturation in preterm infants restrained in car seats. Preterm infants reaching 34 to 35 weeks' gestation were studied at the week of discharge in 3 different conditions for 20 minutes each time: supine decubitus, sitting position in a newborn car seat, and sitting position in the car seat equipped with an apparatus that supports the head, while monitored by pulse oxymetry. Data are expressed as percent of time over each period during which the oxygen saturation was below 90, 92, 94, or 96%. Statistical analysis was by analysis of variance (ANOVA) followed by paired Student t-test for differences of means. There were no significant differences among groups in percent of time with oxygen saturation below 96, 94, 92, or 90%. Oxygenation is not improved in relatively healthy preterm infants placed in a car seat when their head is supported to prevent lateral movements by a special apparatus.