SAN FRANCISCO – Prophylactically placing a pessary around the cervix during the second trimester reduces the risk of preterm birth in women with a multiple pregnancy who have a shorter cervix, a randomized trial conducted in the Netherlands has shown.
Pessaries were ineffective when compared with usual care among the entire population of 813 women with a multiple pregnancy studied, according to data reported at the annual meeting of the Society for Maternal-Fetal Medicine.
Dr. Sophie Liem
But among the subgroup with a cervix measuring less than the 25th percentile – which corresponded to 38 mm in the study population – the use of pessaries cut the risk of a composite of poor perinatal outcomes by 60%, the risk of death before discharge by 86%, and the risk of delivery before 32 weeks by 51%.
"In unselected women with a multiple pregnancy, prophylactic use of a pessary does not reduce poor perinatal outcome. However, in women with a multiple pregnancy and a cervical length below 38 mm at 16-22 weeks, the pessary reduced both poor perinatal outcome and preterm birth rates," commented lead investigator Dr. Sophie Liem, an ob.gyn. with the Academic Medical Center in Amsterdam.
Attendee Dr. B. Anthony Armson of Dalhousie University in Halifax, N.S, commented, "Most of us would consider 38 mm normal length. I wonder if you were to extrapolate that into a recommendation, would you have us all identify what our 25th percentile is or select our usual standard of less than 25 mm?
"Initially, we planned a subgroup analysis for women with a cervical length below 25 mm." However, "we found we had only nine women with a cervical length below 25 mm. So prior to analysis, we changed the cutoff to the 25th percentile," Dr. Liem explained. "I don’t know if the distribution of the cervical length in the United States would be the same as in the Netherlands."
An attendee from Houston noted, "When I put a pessary in pregnant women, one of the things is that they are not having sex. Did you assess sexual activity in those in the placebo group versus those in the pessary group? Do you think this might be related to sexual activity because those with the pessary were not having sex, compared to those in the placebo group?"
"Unfortunately, we didn’t record sexual behavior, so we do not have data on that," Dr. Liem replied.
Attendee Dr. Arnold Cohen of the Einstein Medical Center in Philadelphia, said, "The [Arabin] pessary that was used, from the diagram, seems to be circular around the cervix. That isn’t the type of pessary we use in the United States routinely. Can you comment on whether it was basically a cerclage effect of what you used, or would other pessaries work in the same way?"
"The exact working mechanism is not known," Dr. Liem said. "It has been hypothesized that the pessary changes the angle of the cervical canal and therefore maybe pressure on the internal os, and prevents deterioration of the cervical mucous plug or the loss of it. I don’t know if other pessaries would work the same."
Providing some background to the study, she noted that previous research has shown that progestagens, bed rest, and cerclage are all ineffective for preventing preterm birth in multiple pregnancies. "Several studies suggest that the pessary could prevent preterm birth; however, most studies were small and not randomized," she said.
Women enrolled in the new study, known as the ProTWIN trial, had a multiple pregnancy (monochorionic or dichorionic) with a gestational age of 12-20 weeks. They did not have fetuses with congenital disorders, stillbirth, twin-to-twin transfusion syndrome, or placenta previa.
The women were randomized evenly to placement of an Arabin pessary at 16-20 weeks or usual care. In the former group, the pessary was removed at 36 weeks, or earlier in the case of premature rupture of membranes, vaginal bleeding, severe painful contraction, or other discomfort.
Overall, 55% of the women were nulliparous, and 6% had a previous preterm delivery, Dr. Liem reported. The mean cervical length was 44 mm.
In the trial population as a whole, the rate of the primary outcome – a composite of eight adverse perinatal outcomes – was 13% in the pessary group and 14% in the usual care group, a nonsignificant difference. The pattern was the same for each component individually.
The two groups were also statistically indistinguishable with respect to the time to delivery, the number of days spent in the neonatal intensive care unit, and various measures of maternal morbidity.