Preterm birth is a major public health problem worldwide: 9–12% of babies are born prematurely. Preterm birth contributes to perinatal mortality and morbidity, hospital admission during childhood, cerebral palsy and other neurological disorders, learning abnormalities, long-term respiratory morbidity, and other complications. Current strategies to prevent preterm birth include intramuscular 17α-hydroxyprogesterone which has had modest success in subgroups of women with a singleton pregnancy if they have had a previous preterm delivery, as has vaginal progesterone when a short cervix is noted in the second trimester. Cerclage decreases the risk of premature birth in some women with a singleton pregnancy.
Women with a multiple pregnancy are one of the highest risk groups for preterm birth. Efforts to decrease the frequency of preterm birth in women with a multiple pregnancy are plagued by a scarcity of data supporting interventions. This open-label randomised control trial reports the results of Arabin pessary placement at 16–20 weeks' gestation versus no prophylactic treatment in 813 women with a multiple pregnancy. The Arabin pessary is made of soft flexible silicone and is available in 6 different sizes. The trial was done in 40 centres in the Netherlands and randomisation was stratified by hospital. The primary outcome was a composite of poor perinatal outcome: stillbirth, periventricular leucomalacia, severe respiratory distress syndrome, bronchopulmonary dysplasia, intraventricular haemorrhage, necrotising enterocolitis, proven sepsis, and neonatal death. Analyses were by modified intention to treat. The authors report that prophylactic use of a cervical pessary did not improve perinatal outcomes (relative risk [RR] 0.98, 95% CI 0.69–1.39). However, in women with a multiple pregnancy and a cervical length of less than the 25th percentile (38 mm), the pessary did reduce the frequency of poor perinatal outcomes (RR 0.40, 95% CI 0.19–0.83; P=0.0106) and increased gestational age at delivery (hazard ratio 0.49, 0.32–0.77; P=0.0437). Additionally, the pessary reduced the proportion of women with a monochorionic pregnancy who had a poor perinatal outcome (RR 0.53, 0.28–0.99).
An accompanying editorial notes the following limitations with this study:
• The authors planned a secondary analysis of women with a short cervix, but the threshold changed from less than 25 mm to less than the 25th percentile early in the study, when too few women met the initial absolute criterion for a short cervix.
• Unfortunately, the trial protocol did not stipulate cervical length measurements at enrolment, meaning that data are missing for 75 (19%) of 403 women in the pessary group and 117 (29%) of 410 in the control group. These data gaps represent a missed opportunity to answer definitively the question of the role of cervical length in response to pessary treatment.
• The subgroup analysis of women carrying monochorionic twins was secondary.
• Pessary use is associated with maternal difficulties. The pessary was removed before 36 weeks' gestation in 186 (46%) of 401 women included in the analysis and removal was often followed by delivery within 48 hours. Frequencies of preterm prelabour rupture of membranes (9% of women in the pessary group vs. 8% in the control group), endometritis (<1% in both), urinary tract infection (1% vs. 0%), chorioamnionitis (3% in both), and venous thromboembolism (1% vs. <1%) were similar in both groups. 104 (26%) of women in the pessary group had vaginal discharge.
Despite the need for careful selection and counselling of patients, the authors have provided data to support use of Arabin pessaries to avoid or delay preterm delivery in women with a fairly short cervix and a multiple pregnancy early in the second trimester.