Relationship between mechanical properties of the uterine cervix and occurrence of postdate pregnancy.

Postmaturity is associated with an increased risk of fetal distress and of intrauterine fetal death. In order to assess the probability of the occurrence of postdate delivery, we have determined the Bishop score and measured the cervical distensibility index (CDI) using a cervicotonometer in 52 normal pregnant primiparous women between 37 and 40 weeks of pregnancy. 16 out of the 52 patients delivered after 41 weeks.