Personalized assessment of cervical length improves prediction of spontaneous preterm birth: a standard and a percentile calculator.

Abstract Background A sonographic short cervix length ( Objectives 1) To create a customized cervical length standard that considers relevant maternal characteristics and gestational age at sonographic examination and 2) to assess whether customization of cervical length evaluation improves the prediction of spontaneous preterm birth. Methods This retrospective analysis comprises a cohort of 7,826 pregnancies enrolled in a longitudinal protocol between January 2006 and April 2017 at the Detroit Medical Center. Study participants met the following inclusion criteria: singleton pregnancy, one or more transvaginal sonographic measurements of the cervix, delivery after 20 weeks of gestation, and available relevant demographics and obstetrical history information. Data from women without a history of preterm delivery or cervical surgery who delivered at term without progesterone treatment (N=5,188) were used to create a customized standard of cervical length. Prediction of the primary outcome, spontaneous preterm birth Results The median cervical length remained fundamentally unchanged until 20 weeks of gestation and subsequently decreased non-linearly with advancing gestational age among women who delivered at term. The effects of parity and maternal weight and height on the cervical length were dependent on the gestational age at ultrasound scan (interaction, p Conclusions Compared to the use of cervical length