For women at increased risk of preterm birth, obstetricians have a few tricks up their sleeves to reduce that risk. Depending on the individual circumstances, progesterone injections or pills, a stitch in the cervix (called a cervical cerclage), or a plastic ring around the cervix (called a cervical pessary), may all help delay a preterm birth. But all of these interventions work under one condition: if the woman has a singleton pregnancy.
What about twin pregnancies? Twin pregnancies are at significantly increased risk of preterm birth. Only 1.5% of pregnancies are twins, but 25% of all preterm births occur in twin pregnancies. That’s quite the increased risk! Researchers and doctors have long hoped to find a treatment or intervention that would help out twins. Prior research has explored progesterone and cervical cerclage, and neither has been useful for twins. In the January 2016 Gray Journal, Dr. Nicolaides and his group of doctors and researchers at King’s College in London, published a “Report of Major Impact” testing out the last of the three interventions: cervical pessary for twin preterm birth prevention.
What exactly is a pessary? We usually think of pessaries for the treatment of prolapse, which usually occurs in post-menopausal women, not pregnant women. With prolapse, some of the internal organs give out to gravity and move downwards. A pessary is a little plastic device that is inserted into the vagina to help keep the organs in place. There are tons of different designs and configurations- from disks to cubes to tubes. The pessaries in this trial were similar but different- they were plastic rings that fit snugly around the cervix in the hopes that they would help keep the cervix closed and prevent a preterm birth (which requires the cervix to dilate open, as it should in labor).
The researchers conducted a randomized, controlled trial. 1,180 women with twin pregnancies signed up to participate. Half of them were randomly assigned to have a cervical pessary placed at 20 to 24 weeks of pregnancy (the treatment arm), and half were randomly assigned to have no intervention (the control arm). The pessary stayed in place until 37 weeks of pregnancy unless it caused significant discomfort or there was another reason to remove it, such as bleeding or preterm labor. 31 women (5%) had the pessary removed early due to discomfort.
The authors mainly wanted to know if the pessaries would decrease spontaneous preterm births before 34 weeks gestation. Unfortunately, there was no difference in spontaneous preterm birth <34 weeks gestation. The group of women who received pessaries had a preterm birth rate of 13.6%, and the women who received no pessary had a preterm birth rate of 12.9%, not significantly different.
The researchers also looked at a number of secondary outcomes. The first of these outcomes was perinatal death, which was also essentially the same in the two groups: 2.5% and 2.7%. The next secondary outcome was a composite score of complications for the baby. These included: bleeding in the brain (intraventricular hemorrhage), breathing problems (respiratory distress syndrome), an eye problem related to prematurity (retinopathy of prematurity), and bowel problems (necrotizing enterocolitis). Again, there was no significant difference between the two groups, 10% and 9.2%. Finally, the researchers compared the neonates’ need for various therapies, including ventilation, phototherapy, antibiotics for sepsis, or blood transfusion. Yet again, there was no difference, 17.9% and 17.2%.
The authors finally conducted a small subgroup analysis on the women most likely to benefit- women with short cervixes, an additional risk factor for preterm birth on top of having a twin pregnancy. Of the 214 women with a short cervix, again no benefit emerged from the use of a cervical pessary.
The results are certainly disappointing; we are all holding out for a win on the twin pregnancy preterm birth prevention front. Unfortunately, this excellently designed and executed study does not support the use of cervical pessary in twin pregnancies.