The use of antenatal steroid ( OR 0.5 , 95 % CI 0.3-0 .9 ) and postnatal probiotic ( alone or in synbiotic ) ( OR 0.5 , 95 % CI 0.2-0 .8 ) decreased the risk of NEC , and maternal antibiotic exposure increased this risk ( OR 1.9 , 95 % CI 1.1-3 .6 ) .