To estimate prevalence of car safety seat (CSS) misuse for newborns on hospital discharge; and to identify potential risk and protective factors for CSS misuse.

We randomly sampled 291 mother–baby dyads from the newborn unit of an academic health center. Participants completed a survey and designated someone (themselves or another caregiver) to position their newborn in the CSS and install the CSS in their vehicle. Certified child passenger safety technicians assessed positioning and installation using nationally standardized criteria. To examine factors associated with CSS misuse, we used logistic regression to compute ORs and 95% CIs.

A total of 291 families (81% of those eligible) participated. Nearly all (95%) CSSs were misused, with 1 or more errors in positioning (86%) and/or installation (77%). Serious CSS misuse occurred for 91% of all infants. Frequent misuses included harness and chest clip errors, incorrect recline angle, and seat belt/lower anchor use errors. Families with mothers of color (OR, 6.3; 95% CI, 1.8-21.6), non-English language (OR, 4.9; 95% CI, 1.1-21.2), Medicaid (OR, 10.3; 95% CI, 2.4-44.4), or lower educational level (OR, 4.5; 95% CI, 1.7-12.4) were more likely to misuse CSSs. However, families that worked with a child passenger safety technician before delivery were significantly less likely to misuse their CSSs (OR, 0.1; 95% CI, 0.0-0.4).

Nearly all parents of newborn infants misused CSSs. Resources should be devoted to ensuring families with newborns leave the hospital correctly using their CSS.