Interim analysis unfavorable to continue the study

Placing a cervical pessary in severe twin-to-twin transfusion syndrome (TTTS) cases treated by fetoscopic laser coagulation (FLC) decreases the spontaneous preterm birth rate.

Monochorionic (MC) twin pregnancies present with a high rate of fetal complications, most of them associated with the placental vascular anastomoses. Fetoscopic laser coagulation (FLC) is a surgical technique that allows minimally invasive access into the uterus and has emerged as a useful tool in the management of the most common and severe of these complications, twin to twin transfusion syndrome (TTTS). Even though, preterm birth remains a common cause of adverse outcome because TTTS is associated with a 29% risk of delivering before 28 weeks.

A short cervical length (CL), defined as a CL ≤ 25 mm, detected by transvaginal ultrasound is an independent risk factor for preterm birth in twin pregnancies but no effective treatment has been described to prevent it.

Although is usually accepted that in twin pregnancies cerclage may increase the risk of preterm birth, Salomon and co-workers, found that in cases of TTTS with a CL below the 5th percentile (15 mm) at the time of surgery, performing an emergency cerclage prolonged the pregnancy and allow for better outcome, But still preterm birth after FLC remains a big challenge, so new methods to prevent it must be investigated.

Previous studies in singletons and twins have shown that the use of cervical pessary significantly reduces the frequency of birth before 32 weeks and prolongs pregnancy. The advantage of using cervical pessary is that it is less invasive than cerclage and can be removed easily. That's the reason why pessaries could be considered an alternative, non invasive option to prevent preterm birth in cases of twin to twin transfusion syndrome (TTTS) treated by laser surgery.

Inclusion Criteria:

• Monochorionic twin pregnancies with severe TTTS requiring intrauterine surgery
• Less than 26 weeks
• Minimal age of 18 years
• Informed consent signature

Exclusion Criteria:

• Major fetal abnormalities (requiring surgery or leading to infant death or severe handicap)
• Cerclage prior to randomisation
• Uterine malformation
• Placenta previa
• Active vaginal bleeding at the moment of randomization
• Spontaneous rupture of membranes at the time of randomization
• Death of both twins after the surgery
• Monochorionic-monoamniotic twin pregnancy
• Silicone allergy
• Current participation in other RCT