My Daugther Had A Baby 1 Wk Ago.they Sent Her

my daugther had a baby 1 wk ago.they sent her home the next day. 4days later she was rushed back to hospital bleeding badly. they did dnc and gave her blood.they said placenta was not compleatly shed .they said if she dont get better they will have to do hestorectomy
.how could this have happened.