Cerclage Plus Progesterone vs Progesterone Alone in Twin Short Cervix

This study aims to compare the effectiveness of cervical cerclage combined with progesterone versus progesterone alone in preventing preterm birth among women with twin pregnancies and a short cervix (cervical length ≤ 30 mm). Participants will be randomly allocated to either the intervention group (cerclage plus progesterone) or the control group (progesterone alone).

The incidence of multiple pregnancies has increased rapidly over the years mainly due to the resultant widespread use of assisted reproduction techniques. The twin birth rate in the USA has risen 70%, from 19 per 1000 live births in 1980 to 31 per 1000 live births in 2020. Twin pregnancies have a high risk on preterm birth (PTB) which is associated with increased risk of neonatal mortality and long-term morbidity. Around 60% of twin pregnancies deliver prior to 37 weeks and 12% before 34 weeks of gestation, with rates 5 and 8 times higher than the equivalent rates for a singleton pregnancy, respectively. Children born at an early gestational age are at increased risk of short-term morbidities affecting vital organ systems such as lungs, brain, bowels and are at increased risk of severe infection and sepsis. Perinatal mortality is strongly associated with extreme PTB. Survivors are at increased risk for developmental and behavioral disorders. In Vietnam, the rate of twin pregnancies deliver at \< 28 weeks was about 11% in 2019. Caring for extremely premature infants is a significant burden for families and society. Therefore, obstetricians have a need for high-quality evidence for effective treatments. Cervical length measurement (ideally transvaginal) is the preferred method of screening for preterm birth in twins; 25mm is a pragmatic cut-off between 18 and 24 gestational weeks (Grade of recommendation: C). Majority of the studies conducted previously has taken the cut-off cervical length as ≤ 25 mm. A systematic review and meta-analysis (13 retrospective studies and 3 RCTs) showed that cervical cerclage may reduce preterm birth in twin pregnancies with a cervical length \<25 mm; however, preterm birth before 37, 34, and 28 weeks remained high (56.7%, 38.8%, and 11.7%, respectively)5, compared with much lower rates in singleton pregnancies (6.2%, 4.7%, and 0.4%). These findings support the need for further studies on preterm birth prevention in twin pregnancies with a cervical length \>25 mm. In 2025, Yen et al. showed that cervical cerclage was more effective than pessary in twin pregnancies with a cervical length ≤28 mm, particularly in reducing preterm birth \<28 weeks, with benefit observed at 25-28 mm. However, preterm birth rates remained high, suggesting that intervention at a higher cervical length threshold may be justified. Given gestational age-related cervical shortening and the substantially higher preterm birth risk in twins, a higher threshold corresponding to the 10th percentile (≤30 mm) has been proposed. Accordingly, we selected ≤30 mm as the intervention threshold in twin pregnancies. In singleton pregnancies, vaginal progesterone is recommended as the primary intervention for pregnant women with a cervical length less than 25mm with consistently demonstrated effectiveness in preventing premature labor. In cases with a prior spontaneous preterm delivery and a short cervix, the placement of a vaginal cerclage should be conside trial.show_full_description

Inclusion Criteria: * Maternal age ≥ 18 * Twin pregnancy * Asymptomatic short cervix (CL≤30mm) at routine ultrasound investigation * Gestational age at 16+0- 24+0 weeks Exclusion Criteria: A potential paticipant who meets any of the following criteria will be excluded from participation in this trial: * Women with twin pregnancy in which one or both fetuses are diagnosed with a major structural or congenital abnormality that is likely to influence the composite adverse neonatal outcome. * Women with a monochorionic monoamniotic twin pregnancy * A monochorionic twin pregnancy with twin-to-twin transfusion syndrome before or at the time of inclusion. * Patients have indications for vaginal cerclage: Recurrent late miscarriage (from 14 weeks) or preterm birth occurring two or more times. * Women with dilatation of the cervix diagnosed by ultrasound or physical exam * Women with overt symptoms of preterm labor at the time of measurement of the short cervix (regular contractions, PPROM, recurrent blood loss). * Women with the presence of fever ≥ 38 degrees Celsius. * Women with a placenta previa, vasa previa. * Uterine malformations: unicornuate uterus, bicornuate uterus, uterine septum, fibroid… * Severe maternal conditions (heart failure, chronic kidney disease, systemic lupus erythematosus …)