Abstract: We included two trials that recruited a total of 234 women. The overall risk of bias was low for the two studies. Both studies compared Bishop score withTVUS. The two included studies did not show any clear difference between the Bishop score and TVUS groups for the following main outcomes: vaginal birth (RR 1.07, 95% CI 0.92 to 1.25, moderate quality evidence), caesarean delivery (RR 0.81, 95% CI 0.49 to 1.34, moderate quality evidence), neonatal admission into neonatal intensive care unit (RR 1.67, 95% CI 0.41 to 6.71, moderate quality evidence). Both studies only provided median data in relation to induction-delivery interval and reported no clear difference between the Bishop and TVUS groups. Perinatal mortality was not reported in the included studies. For the review's secondary outcomes, the need for misoprostol for cervical ripening was more frequent in the TVUS group compared to the Bishop score group (RR 0.52, 95% CI 0.41 to 0.66, two studies, 234 women, moderate quality evidence). In contrast, there were no clear differences between the Bishop scope and TVUS groups in terms of meconium staining of the amniotic fluid, fetal heart rate abnormality in labour, and Apgar score less than seven. Only one trial reported median data on the induction-delivery interval and induction to active phase interval, the trialist reported no difference between the Bishop group and the TVUS group for this outcome. Neither of the included studies reported on uterine rupture. Moderate quality evidence from two small RCTs involving 234 women that compared two different methods for assessing pre-induction cervical ripening (Bishop score and TVUS) did not demonstrate superiority of one method over the other in terms of the main outcomes assessed in this review. We did not identify any data relating to perinatal mortality. Whilst use of TVUS was associated with an increased need for misoprostol for cervical ripening, both methods could be complementary. The choice of a particular method of assessing pre-induction cervical ripening may differ depending on the environment and need where one is practicing since some methods (i.e. TVUS) may not be readily available and affordable in resource-poor settings where the sequelae of labour and its management is prevalent. The evidence in this review is based on two studies that enrolled a small number of women and there is insufficient evidence to support the use of TVUS over the standard digital vaginal assessment in pre-induction cervical ripening. Further adequately powered RCTs involving TVUS and the Bishop score and including other methods of pre-induction cervical ripening assessment are warranted. Such studies need to address uterine rupture, perinatal mortality, optimal cut-off value of the cervical length and Bishop score to classify women as having favourable or unfavourable cervices and cost should be included as an outcome.

Plain-language summary: Moderate quality evidence was available from the two included studies which compared the Bishop score with transvaginal ultrasound (TVUS) (ultrasound done through the vagina). The studies were considered to be at a low risk of bias. The need for misoprostol (a drug) for softening the cervix (cervical ripening) was more common in the TVUS arm. No clear difference was seen between the two methods in terms of vaginal birth, caesarean delivery, admission of the newborn into the neonatal intensive care unit, meconium staining of the amniotic fluid, abnormal heart beat of the baby within the womb whilst the mother was in labour and Apgar score less than seven (difficulty of the baby establishing life and other life movements on its own immediately after childbirth). None of the included studies reported on tears of the womb or death of the baby just before, during or immediately after childbirth. We did not find any studies that compared Bishop score with any other methods such as the presence of vaginal fetal fibronectin or insulin-like growth factor binding protein-1. Authors conclusions Although the overall quality of evidence is moderate, there is no difference in outcomes between the two methods (Bishop score and TVUS) apart from the increased need of misoprostol in the TVUS group. Both methods could be useful to each other, or complementary as the Bishop score does not need any special equipment and uses digital examination which is required to induce labour (to insert a cervical ripening agent, rupture the membranes or separate them from the cervix) but TVUS can give additional information that may affect the course and management of the labour. The choice of a particular method may differ depending on the environment and need since TVUS requires training and may not be readily available and affordable in resource-poor countries. Future research  The two included studies involved a small number of women and further studies are needed. Such studies should include outcomes such as rupture of the womb, perinatal mortality, most appropriate cut-off value for the cervical length and Bishop score to classify women as having ripe or unripe cervices, and cost.