Having twins accounts for only 1.5% of all births but 25% of preterm births, the leading cause of infant mortality worldwide. Successful strategies for reducing singleton preterm births include prophylactic use of progesterone and cervical cerclage in patients with a prior history of preterm birth. To investigate whether the use of a cervical pessary might reduce premature births of twins, an international team of researchers conducted a large, multicenter, international randomized clinical trial (RCT) of approximately 1200 twin pregnancies. They report in the American Journal of Obstetrics & Gynecology that placement of a cervical pessary did not reduce spontaneous preterm births or reduce neonatal complications.
The rates of preterm birth (defined as <37, <34, or <32 weeks) are 5-6 times higher in twin than in singleton gestations. A cervical pessary is a plastic device that can be placed around the cervix in order to keep it closed and "long" in the hope that it will prevent preterm delivery.
"Twin pregnancies are at substantially higher risk of early preterm birth than singleton pregnancies and this risk is inversely related to sonographically measured cervical length at 20-24 weeks' gestation," explained lead investigator Kypros H Nicolaides, MD, Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London. "Our research indicates that insertion of cervical pessary at around 22 weeks in both randomly selected women pregnant with twins and in patients with a short cervix of less than 25 millimeters does not reduce the rate of spontaneous early preterm birth, perinatal death, adverse neonatal outcome, or need for neonatal therapy."
1180 women pregnant with twins participated in this multicenter RTC (centers in Europe, Asia, and South America), one of the largest studies ever conducted in twin gestations. 590 patients received cervical pessaries while 590 had expectant management. There were no significant differences between the pessary and control group in rates of spontaneous birth at less than 34 weeks (13.6% vs. 12.9%), perinatal death (2.5% vs. 2.7%), adverse neonatal outcome (10.0% vs. 9.2%), or neonatal therapy (17.9% vs. 17.2%).
Two RCTs published after the start of this study provided contradictory results on the effect of cervical pessary on the rate of spontaneous birth at <34 weeks in singleton pregnancies with short cervix. Dr. Nicolaides and co-investigators conducted a post hoc subgroup analysis of 214 women with short cervix (<25 mm), which also showed no benefit from the insertion of a cervical pessary.
"This is a major international study examining an important clinical question - namely, whether a cervical pessary can reduce the rate of preterm delivery in twin gestations," commented Roberto Romero, MD, DMedSci, Editor-in-Chief for Obstetrics of the American Journal of Obstetrics and Gynecology, and Chief of the Perinatology Research Branch of NICHD/NIH. "Importantly, a cervical pessary did not reduce the rate of preterm delivery in women with either a short or long cervix. The report is key because many had hope that placement of this doughnut-like device would prevent preterm delivery. The results can be used to focus research on other therapeutic interventions that may be more effective in preventing preterm delivery in twin gestations."