Summer used to mean carefree days laying out by the pool – but as a new mom, you're now more concerned about your baby's safety in the heat. Overdress a baby and he could develop an angry heat rash. Expose his fragile body to hot conditions and he could be vulnerable to a painful sunburn or to heatstroke, a serious affliction characterized by a high fever and rapid breathing. Overheating has also been linked to sudden infant death syndrome (SIDS), a fatal sleeping disorder. "Babies sleep deeply when they're hot, making them difficult to arouse, which may increase the risk of SIDS," explains Bruce Epstein, M.D., a pediatrician in Pinellas Park, Florida.