Foley Bulb Insertion by Blind Placement Compared With Direct Visualization: A Randomized Controlled Trial

To test the hypothesis that digital placement of a balloon catheter is not inferior to the speculum method in terms of rate of maternal infection.

In an open-label noninferiority randomized trial, pregnant women who were undergoing induction of labor with unfavorable cervix (less than 3 cm dilated and less than 60% effaced) were randomly assigned to balloon catheter that was placed either digitally or using a sterile speculum. The primary outcome was a composite of maternal infection, defined by occurrence of fever (temperature 38°C or higher), chorioamnionitis, or endometritis (diagnoses were made by the managing obstetric physician or midwife). Prespecified secondary outcomes included outcomes in the primary composite, cesarean delivery rates, and maternal and neonatal outcomes. A patient satisfaction survey was also obtained. On the basis of a noninferiority margin of 10% and an expected primary outcome frequency of 10%, a sample size of 372 women was needed (90% power to confirm noninferiority with 90% protocol adherence).

From February 2018 through February 2019, 372 women were randomized (185 digital placement, 187 sterile speculum). Baseline characteristics were similar between groups. The composite maternal infection rate was not different between groups (digital placement arm: 15.7% vs speculum arm: 12.8%), with an absolute difference with respect to the sterile speculum arm of 2.8% (95% CI -4.3 to 9.9%), indicating noninferiority for the prespecified margin. Secondary outcomes were not different between groups, except for a higher need for a second balloon catheter in the sterile speculum arm. Maternal and neonatal adverse events were not different between groups. Irrespective of method of placement, women were equally satisfied with the explanation of the method before placement, anxiety regarding the procedure, and pain during placement. More women in the sterile speculum group would choose the digital placement method for the subsequent pregnancy (37.6% vs 25.7%; P=.02.).

Digital placement of a balloon catheter for preinduction cervical ripening is noninferior to the sterile speculum method, in terms of maternal infection. Women in the sterile speculum group more frequently required a second round of the mechanical dilator. The blind digital approach is a reasonable option for balloon placement for cervical ripening.

ClinicalTrials.gov, NCT03450408.