Familial occurrence of sudden infant death syndrome and apnea of infancy.

We sought to determine the outcome of infants born to families with multiple victims of sudden infant death syndrome (SIDS) and/or apnea of infancy. Seventy-three infants, born to families who had two or more previous siblings who had either died of SIDS or who were monitored at home for apnea of infancy or for abnormal results on polysomnogram and/or pneumogram recording, were prospectively monitored. The infants underwent polysomnogram and pneumogram recordings and were subsequently monitored at home with a cardiorespiratory monitor. All episodes of apnea were immediately reviewed. Thirteen infants (18%) had subsequent severe episodes of apnea and five other infants (7%) died during a subsequent episode. All deaths occurred in families who had two or more SIDS victims. The outcome for the 17 infants who were half siblings was similar to the outcome for full siblings. Clinical data of the infants and results of evaluation were not predictive of outcome.