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Rates of preterm birth were lower among women with short cervical length and without prior preterm birth, who used a cervical pessary -- a silicone device used to prevent spontaneous preterm birth -- in a 300-patient randomized trial.

Compared to a control group who did not receive a pessary in the open-label study, the rate of spontaneous preterm birth at less than 34 weeks gestation was significantly lower among women who received a pessary (15.3% versus 7.3%, respectively, P=0.04), reported Gabriele Saccone, MD, of the University of Naples in Italy, and colleagues.

Rates of spontaneous preterm birth at less than 37 weeks gestation were also significantly lower for the pessary group versus controls (20.0% versus 32.7%, respectively, P=0.02), but not at less than 32 or 28 weeks gestation, the authors wrote in the .

They noted that the cervical pessary was examined in prior with including a that found no impact on rates of spontaneous preterm birth or perinatal outcomes.

Notably, they discussed the large trial in the U.K. that was published last March, but noted it was "methodologically very different from our study," because it included women with prior preterm birth, had multiple study sites and unlike this trial, hands-on training was not required to "demonstrate pessary insertion competence."

An from Robert Silver, MD, of the University of Utah, and Ware Branch, MD, of Intermountain Health Care in Salt Lake City, argued there was an important difference in cervical length between the two trials. While the prior large study had a mean cervical length of 20 mm, this trial had a mean cervical length of about 12 mm.

"The shorter the cervix, the higher the risk of preterm birth, and the shorter cervical lengths in [this] study ... may reflect a unique population referred to a single tertiary care center," the editorialists wrote. "Thus, the results may not be generalizable to women with relatively less short cervical lengths."

Saccone and colleagues conducted a single-center randomized trial of women with asymptomatic singleton pregnancies, without a prior spontaneous preterm birth. Short cervical length was determined via transvaginal ultrasound. Women were ages 18 to 50 years old with a cervical length of 25 mm or less. Gestational age at randomization was from 18 weeks to about 24 weeks.

Of the 300 women, 150 were randomized to receive a cervical pessary and 150 were randomized to a usual-care control group. Over 80% in both the pessary and control groups had a cervical length of under 20 mm and received vaginal progesterone. About a quarter from each group received antibiotics due to positive cultures from a vaginal swab.

Mean gestational age at randomization was around 22 weeks, with a mean cervical length of 11.5 mm (pessary) and 12.5 mm (control).

While the difference in spontaneous preterm birth was significant for women at less than 34 and 37 weeks gestation, it was non-significant at less than 32 weeks gestation (6.7% pessary versus 9.3% control, P=0.52) and at less than 28 weeks gestation (4.0% versus 6.0%, P=0.60).

Examining adverse events, there was a higher rate of increased or new vaginal discharge in the pessary group versus controls (86.7% versus 46.0%), but there were no significant differences in pelvic discomfort, the authors said.

Limitations to the data included the open-label nature of the trial and that secondary outcomes and endpoints "with no adjustment for multiple comparisons could have led to type 1 error," they wrote.

Silver and Branch stressed that there are many proposed interventions to prevent preterm birth, but clinicians should accept while these interventions are "well-intentioned," there is not one intervention that will work for all patients.

"It is possible, however, to counsel and treat women using the best available data regarding pessary, cerclage, and progestagens while acknowledging the uncertainties regarding efficacy," the editorialists wrote.