Subthreshold phototherapy during the birth hospitalization is effective in preventing readmissions for phototherapy, according to a recent study, however, for each readmission prevented, many newborns require phototherapy who would otherwise not need it. Researchers conducted a retrospective cohort study of 25,895 newborns born at ≥35 weeks’ gestation in 1 of 16 Kaiser Permanente Northern California hospitals from January 1, 2010, through December 31, 2014, with at least 1 total serum bilirubin (TSB) level from 0.1 to 3.0 mg/dL below the appropriate American Academy of Pediatrics (AAP) phototherapy threshold and not exceeding the threshold during the birth hospitalization. They found:

• Of total newborns with qualifying TSB levels from 0.1 to 3.0 mg/dL below the appropriate AAP phototherapy threshold, 4,956 (19.1%) received subthreshold phototherapy and 241 of these (4.9%) were readmitted for phototherapy compared with 2,690 of 20,939 untreated newborns (12.8%).
• Newborns who received formula feedings had lower adjusted odds of readmission for phototherapy compared with exclusively breastfed newborns.
• Subthreshold phototherapy was associated with a 22-hour longer length of stay.