Effect of a Cervical Pessary on the Rate of Bleeding in Placenta Praevia

Placenta previa and low-lying placenta are important causes of bleeding in the second and third trimesters of pregnancy and are associated with increased risks of hospitalization, preterm birth, cesarean delivery, and maternal and neonatal complications. Current management is mainly expectant and supportive. Additional strategies that may reduce bleeding and help prolong pregnancy could improve outcomes in this high-risk population.

A cervical pessary is a non-surgical silicone device placed around the cervix. It has mainly been used to reduce the risk of preterm birth in selected pregnancies, especially in women with a short cervix. In women with placenta previa or a low-lying placenta, pessary placement may help stabilize the lower uterine segment and reduce mechanical stress near the internal cervical os. This may decrease the frequency of vaginal bleeding and delay the need for delivery. Previous studies have suggested potential benefit, but the available evidence has been limited and inconclusive. This study is intended to provide additional randomized prospective evidence on the effect of cervical pessary treatment in this setting.

This is a prospective, randomized, multicenter, two-arm study. Eligible participants are pregnant women 18 to 45 years of age with a singleton pregnancy and ultrasound-confirmed placenta previa (total or marginal) or a low-lying placenta with the placental edge less than 20 mm from the internal os, diagnosed between 20 and 30 weeks of gestation. Written informed consent is required before enrollment. Patients with multiple pregnancy, fetal malformations or chromosomal abnormalities detected by ultrasound, uterine malformations, silicone allergy, cervical dilation, cervical or vaginal infection, cervical cancer, cervical tears or scarring, ectopic cervical tissue, preterm prelabor rupture of membranes, regular contractions, cerclage, a pessary already in place, active bleeding, or genital prolapse grade III or IV will be excluded. Placenta accreta spectrum is not an exclusion criterion.

Participants will be randomized in a 1:1 ratio to an intervention group or a control group using centralized web-based stratified block randomization. Stratification will be performed by study center and maternal age. Participants assigned to the intervention group will undergo placement of an Arabin pessary by an experienced gynecologist between 20 and 30 weeks of gestation. Pessary position will be monitored by ultrasound, preferably transvaginal ultrasound, at regular 4-week intervals. The pessary will be removed at the onset of labor, before a planned cesarean delivery, or earlier if complications such as infection or intolerance occur. Participants assigned to the control group will receive standard care without pessary placement. Both groups will undergo regular clinical and ultrasound follow-up at comparable intervals until delivery.

The primary outcomes are the rate of vaginal bleeding from study entry until delivery, cesarean delivery due to bleeding, and gestational age at cesarean delivery. In the protocol, vaginal bleeding is defined as blood loss of at least 50 mL per episode. Secondary outcomes include the number of hospital admissions due to bleeding, total number of hospital days until delivery, time from randomization to first bleeding episode, cumulative number of bleeding-free days, change in hemoglobin during pregnancy, preterm birth before 34+0 weeks and at or before 37+0 weeks of gestation, gestational age at birth, rate of emergency cesarean delivery, maternal and fetal morbidity and mortality, uterine artery resistance indices on ultrasound, the proportion of participants in whom placental overlap resolves with exposure of the internal os during pregnancy, and the frequency of or abstinence from sexual intercourse during pregnancy.

Study data will be collected through patient diaries, clinical assessment, ultrasound examinations, and an electronic case report form database. Participants will be followed throughout pregnancy with study assessments approximately every 4 weeks until delivery. A postpartum follow-up visit will take place 6 weeks after delivery to assess complications.

The planned sample size is 190 participants, with 95 participants in each study arm. According to the protocol, this sample size is powered primarily for the endpoint of preterm birth before 34 weeks of gestation. Statistical analyses will include comparison of bleeding rates between groups using chi-square testing, with additional analyses for continuous and categorical secondary outcomes as appropriate. Both intention-to-treat and per-protocol analyses are planned. Subgroup analyses will be performed by maternal age, gestational age at randomization, and study center.

The study will be conducted at multiple centers in Germany and Austria with experience in high-risk obstetrics and the management of placenta previa. Ethical approval will be obtained in accordance with applicable national and local requirements. Written informed consent will be obtained from all participants before study inclusion. Safety monitoring will include assessment of adverse events such as infection, pessary intolerance, and preterm labor. Serious adverse events will be reported in accordance with applicable requirements, and study safety will be overseen by an independent Data Safety Monitoring Board.