Can incompetent cervix cause chorioamnionitis in pregnancy? As in my previous first pregnancy cervix dilated painlessly till 8 cm with slight vaginal bleeding. There were no contractions no pain nothing, only contractions were there while expelling the foetus. And placenta report cited acute chorioamnionitis. And according to doctor this infection can only occur when cervix is already open.. Also one day before miscarriage ultrasound report cited internal os closed with cervical length of 3 cm. And suddenly next day in one single day entire cervix got dilated with no pains. Very much concerned about my future pregnancies.