A device known as a pessary, thought promising for reducing preterm birth risk due to a short cervix, appears no more effective than usual medical care, according to a new study. A pessary is a rounded silicone device that fits around a cervix that has shortened, to keep it from opening and leading to miscarriage or preterm birth. The device is typically removed before the 37th week of pregnancy.

This multicenter randomized trial was conducted by Matthew K. Hoffman, M.D., M.P.H., of the Christiana Care Health System, Newark, Delaware, and colleagues in the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units Network. Findings appear in the Journal of the American Medical Association (JAMA).

Researchers enrolled 544 participants (64%) of a planned sample of 850 expectant people from 16 through 24 weeks of pregnancy at risk for preterm delivery because they had a cervical length less than 20 millimeters as measured by ultrasound. At enrollment, attending physicians could perform cervical cerclage (stitching) or administer the steroid progesterone at their discretion.

Participants were assigned at random to undergo or forego pessary placement or usual care. The researchers designed the study to determine if use of a pessary could reduce the risk of a single primary outcome: delivery or fetal death before 37 weeks.

Study recruitment was stopped early when the researchers could see no real difference between the groups in terms of the overall primary outcome, but the risk of fetal or newborn death appeared unacceptably high in the pessary group. Among those receiving a pessary, the primary outcome occurred in 127 participants (45.5%)—a rate which did not differ significantly from 120 participants (45.6%) in the usual care group. Fetal or infant death occurred with 13.3% in the pessary group and 6.8% of the usual care group.

The authors noted that the usual care group was more likely to receive cerclage, which could have influenced the results.