Can pessaries prevent preterm birth?

Preterm birth (PTB) remains the major cause of neonatal morbidity and mortality. For the vast majority of spontaneous PTBs, the final pathway is opening of the cervix. Pessaries have been proposed since the 1950s as a possible intervention to keep the cervix closed and prevent spontaneous PTB (sPTB).¹ They have the possible advantages of being noninvasive, relatively easy to place and to remove, and inexpensive (usually around $30–$40). But are pessaries safe and do they work for prevention of sPTB?

Types of pessaries

The pessary most studied for prevention of sPTB is the Arabin pessary (http://dr-arabin.de/arabin/e/cerclage.html). Dr Birgit Arabin’s father began to produce rubber pessaries in their garage in the 1950s in Germany. The Arabin pessary is the only such device whose safety and efficacy has been assessed in randomized controlled trials (RCTs).^1-8

The Bioteque pessary (http://www.randjmedical.com/product/cup-pessary/), which is very similar, is available in the United States. It has been studied in 2 RCTs, the results of which will be presented at a meeting of the Society for Maternal-Fetal Medicine in January 2017.

How pessaries might work

The mechanism by which pessaries might work for preventing sPTB is unclear, but there are 2 leading hypotheses. One is that the pessary helps to keep the cervix closed. The other is that the pessary might direct the cervix more posteriorly and thus change the inclination of the cervical canal such that the weight is more directed to the anterior lower segment.¹

How to place a pessary

Proper placement of a pessary for prevention of sPTB might seem easy but it is not if you have not been trained to do this procedure. A pessary is usually inserted with the woman in the lithotomy position. The device is bent and then inserted into the vaginal introitus with the small circle towards the patient. Then the operator’s fingers help gently place the pessary, which is now open in the vagina, snug against the fornices, and in particular, push the posterior caudal part of the device towards the posterior fornix.

The fingers should also ensure that the smaller circle of the pessary is around the cervix, with the external os palpable through the small pessary circle. Improper placement can cause a pessary to be ineffective, and maybe even harmful.

How to assess the cervix with a pessary in place

With a pessary in place, it is difficult to assess the cervix by either digital examination or by transvaginal ultrasound (TVU). Experts suggest leaving the device in place if at all possible, unless the membranes are ruptured, or significant cervical dilatation is expected.¹

In cases of rupture of membranes (ROM), most experts recommend permanent removal of the device.¹ While some clinicians have reported successfully imaging the cervix with a pessary in place, that is not easy to do.⁹

Safety issues

Use of pessaries for prevention of sPTB has been studied in thousands of patients.^3-8 Although almost all of these patients experienced an increase in discharge, use of the devices in pregnancy has not been reported to be associated with serious maternal or perinatal complications.

Recommended: Routine certival length screening to prevent PTB

In general, no reports exist of an association between pessary use and increased incidence of vaginal infections. In very rare cases, venous thromboembolism of the cervix, lacerations, strangulation of the cervix, fistulas, bleeding, urinary retention, and other complications have been reported.¹⁰

Evidence for efficacy

Several RCTs have evaluated the safety and efficacy of pessary use for prevention of sPTB. These trials have focused on 3 main populations: singletons with short TVU cervical length (CL); twins, unselected; and twins with short TVU CL (Table).

Singletons with short TVU CL

So far, 3 RCTs have been published in the literature on possible complications and effects of a pessary on singleton gestations in women with a short TVU CL.^3-5 All used the Arabin pessary, and a short TVU CL ≤ 25 mm before 25 weeks’ gestation as criteria for inclusion. While the first published RCT from Spain showed significant benefits in terms of reduced PTB,³ the other 2 trials did not.^4,5 It is unclear why results between studies differed, but some have postulated that better training of operators and, therefore, placement of the pessaries resulted in positive outcomes in 1 trial.

A meta-analysis of the 3 RCTs including 1420 women with a singleton gestation and a short TVU CL ≤ 25 mm before 25 weeks does not show any benefits in terms of PTB or neonatal outcomes of placing an Arabin pessary compared to no pessary (Table). Therefore the data so far do not uniformly support efficacy, hence pessaries should not be used routinely for prevention of PTB until more data become available.

NEXT: What  the studies found about twins

Twins, unselected

Large RCTs including almost 2000 women have shown no benefit from placing a pessary in the second trimester in women with unselected twin gestations, i.e., asymptomatic twins with no other risk factors (not screened for short CL) (Table).^6,7 These data, it appears, are strong enough to conclude that pessaries should not be used prophylactically in twin gestations.

Twins with short TVU CL

So far 3 RCTs have been published in the literature on the safety and effect of pessaries in twin gestations with a short TVU CL.^6-8 All used the Arabin pessary, and mostly a short TVU CL ≤ 25 mm before 25 weeks’  gestation as criteria for inclusion. While 2 RCTs showed significant benefits in terms of reduced PTB,^7,8 the other trial did not.⁶ A meta-analysis of these RCTs including 481 women with twin gestations and a short TVU CL before 25 weeks does not show any benefits in terms of PTB or neonatal outcomes in placing an Arabin pessary compared to no pessary (Table).¹²

Pessaries and other interventions

Evidence is limited regarding comparisons of pessaries with cerclage. The only small, old RCT found no difference in outcomes between the device and the procedure.¹³ A recent retrospective study comparing pessaries to cerclage to expectant management in women with dilated cervices in the second trimester found much better prolongation of pregnancy and decrease in sPTB outcomes in women with physical exam-indicated cerclage, whereas women who received a pessary fared the same as those who were managed expectantly.¹⁴

The evidence so far, therefore, is clearly insufficient to compare pessaries to cerclage. Pessary use has not been shown to be superior in any study, and there is some evidence that the device’s efficacy may be inferior to cerclage.¹⁴

Next: Time to double down on efforts to reduce preterm birth rates

Some have advocated use of pessaries added to other interventions, such as progesterone, for prevention of sPTB. While this approach has clear hypothetical advantages, no study so far has proven cumulative benefit for use of a pessary and progesterone in combination. RCTs are ongoing, and patents have also been proposed for progesterone-releasing pessaries.

Ongoing research

More than 10 RCTs are actively recruiting patients to evaluate the effect of pessaries for prevention of sPTB, mostly in high-risk women with short CLs. A prospective meta-analysis of all ongoing RCTs is being planned, which should be able to analyze in detail any effect in subpopulations, including singletons versus twins, degrees of CL shortening, gestational age at shortening, etc. Another ongoing RCT is comparing efficacy of a pessary to cerclage in women with short CLs.

Summary

While the initial RCT on use of pessaries showed encouraging positive results, 3 the cumulative evidence from RCTs published so far^3-8 does not show any conclusive reduction in incidence of PTB or neonatal morbidity and mortality in either singleton gestations with short CLs, unselected twins, or twins with short CLs (Table).

Because several other RCTs are ongoing, this evidence may change with time. Until the results of these RCTs and the individual patient data meta-analysis are known, pessary use for prevention of PTB should be reserved currently for research trials only, given the lack of efficacy in most of the RCTs published to date.

References

1. Arabin B, Alfirevic Z. Cervical pessaries for prevention of spontaneous preterm birth: past, present and future. Ultrasound Obstet Gynecol. 2013;42(4):390–399.

2. Cross RG: Treatment of habitual abortion due to cervical incompetence. Lancet. 2 (1959) 127.

3. Goya M, Pratcorona L, Merced C et al; Pesario Cervical para evitar prematuridad (PECEP) Trial Group. Cervical pessary in pregnant women with a short cervix (PECEP): an open-label randomised controlled trial. Lancet. 2012;379:1800–1806.

4. Hui SY, Chor CM, Lau TK, Lao TT, Leung TW. Cerclage pessary for preventing preterm birth in women with a singleton pregnancy and a short cervix at 20 to 24 weeks: a randomized controlled trial. Am J Perinatol. 2013;30:283–288.

5. Nicolaides K, Syngelaki A, Poon LC et al. A randomized trial of a cervical pessary to prevent preterm singleton birth. New Engl J Med. 2016 (in press).

6. Nicolaides KH, Syngelaki A, Poon LC et al. Cervical pessary placement for prevention of preterm birth in unselected twin pregnancies: a randomized controlled trial. Am J Obstet Gynecol. 2016;214:3.e1-9.

7. Liem S, Schuit E, Hegeman M et al. Cervical pessaries for prevention of preterm birth in women with a multiple pregnancy (ProTWIN): a multicenter, open-label randomised controlled trial. Lancet. 2013;382:1341–1349.

8. Goya M, de la Calle M, Pratcorona L et al. Cervical pessary to prevent preterm birth in women with twin gestation and sonographic short cervix: a multicenter randomized controlled trial (PECEP-Twins). Am J Obstet Gynecol. 2016;214:145–152.

9. Goya M, Pratcorona L, Higueras T, Perez-Hoyos S, Carreras E, Cabero L. Sonographic cervical length measurement in pregnant women with a cervical pessary. Ultrasound Obstet Gynecol. 2011;38(2):205–209.

10. Arabin B, Halbesma JR, Hubener M, van Eyck. Is treatment with vaginal pessaries an option in patients with a sonographically detected short cervix? J Perinatal Med. 2003;31:122–133.

11. Saccone G, Ciardulli A, Xodo S, et al. Does the cervical pessary prevent spontaneous preterm birth in singleton pregnancies with short cervical length? A systematic review and meta-analysis. J Ultrasound Med. 2017 (in press)

12. Saccone G, Ciardulli A, Xodo S, et al. Does the cervical pessary prevent spontaneous preterm birth in twin pregnancies with short cervical length? A systematic review and meta-analysis. JMFNM. 2017 (in press)

13. Förster F, During R, Schwarzlos G. [Therapy of cervix insufficiency-cerclage or support pessary?]. Zentralbl Gynakol. 1986;108(4):230-237.

14. Gimovsky AC, Suhag A, Roman A, et al. Pessary versus cerclage versus expectant management for cervical dilation with visible membranes in the second trimester. JMFNM. 2016;29(9):1363–1366.