Combined therapy to prevent preterm delivery in high-risk women?

Combined rescue therapy with vaginal progesterone, cervical cerclage and the Arabin cervical pessary may have potential in pregnant women with a short cervical length and a high background risk for preterm delivery. That is the conclusion of a recent retrospective cohort study of singleton pregnancies managed at three tertiary medical centers in Israel between September 2011 and December 2017.

“This combination may prolong their pregnancy and safely bring them near term,” said the authors. However, “additional studies are needed to confirm these preliminary findings.”

The goal of the retrospective cohort study in The Journal of Maternal-Fetal and Neonatal Medicine was to compare the outcome of pregnancy in women with a short cervical length (≤ 25 mm) who were managed by one of four different treatment protocols: vaginal progesterone, cervical cerclage and an Arabin cervical pessary (group A); Arabin cervical pessary and vaginal progesterone (group B); cervical cerclage and vaginal progesterone (group C); or vaginal progesterone alone (group D).

During the study period, 286 pregnant women underwent vaginal ultrasonography between 15 and 29 weeks’ gestation, all with a short cervical length. Group A represented 6.3% (n = 18) of the sample size, Group B 41.9% (n = 120), Group C 31.3% (n = 38) and Group D 38.5% (n = 110). 

A significantly higher portion of patients in group A had either a history of cervical incompetence (44.4% vs. 9.2% in Group B vs. 7.9% in Group C vs. 0.9% in Group D; P = 0.0001) or a cervical procedure (61.1% vs. 37.5% vs. 28.9% vs. 27.3%, respectively; P = 0.027), compared to patients in the other three groups.

However, despite Group A having a shorter cervical length at recruitment-median 14.4 mm (range 0 to 25 mm) versus 15 mm (range 0 to 25 mm) in Group B versus 15.5 mm (range 0 to 25 mm) in Group C versus 19 mm (range 2 to 25 mm) in Group C (P = .002)-the rate of spontaneous preterm delivery (< 37 week’ gestation) was similar across the four groups: 44.4% versus 32.5% versus 36.8% versus 32.7%, respectively (P = 0.665).

This finding suggests that a combined rescue therapy may have a synergistic effect in preventing preterm birth (PTB) in pregnant women with short cervical length and a high risk of PTB, as well as perhaps extending pregnancy and safely bringing these pregnancies to near term.

The mechanisms of action for cervical cerclage are unclear, but it might provide mechanical support to a weakened cervix, plus support the cervical mucosal plug as a barrier to ascending infection. The mechanism allowing a cervical pessary to help prevent PTB has also yet to be fully elucidated. 

One study using MRI noted that the pessary changed the inclination of the cervical canal relative to the uterus and continued to do so, as long as the pessary remained in place. A second study indicated that the pessary might prevent further opening of the internal os caused by the dissociation of amnion and chorion, especially when the pregnant woman is upright.

Furthermore, a review of cervical pessaries for prevention of spontaneous preterm birth proposed that the pessary protects the cervical mucus plug by supporting the attachment of the remaining cervical tissue.