The first 3 months of a baby ' s life are considered the fourth trimester . They need comfort , food , security ALL the time . It can be really exhausting but it will end . CIO is meant to be used for babies who are old enough to not NEED anything when they cry at night . A newborn cries at night because they need something food , a cuddle , a diaper change . You will know when your child is old enough to try CIO which doesn ' t even work for every kid . Certainly didn ' t work for mine . My kid wasn ' t ready to sleep train until about 7 months and then it took 3 months of the chair method but since 12 months we can put her down in her crib awake and leave the room and she goes to sleep . <| sep |> I ' m 99 % sure it ' s character wide . I have way more than 4 legendaries accountwide .