Please select the eligibility criteria that correspond to the clinical trial below.
Title: Canadian Study on the Association of Pessary With Progesterone
Brief Summary: Prematurity is the leading cause of neonatal morbidity causing more than 1 million deaths worldwide per year. In 2012, a randomized controlled trial (RCT) testing "pessary" (silicone ring placed around the cervix) versus "no pessary" in patients with a short cervix showed a 4-fold reduction in the rate of spontaneous prematurity \<34 weeks of gestation and a reduction in perinatal morbidity and mortality. This result was not found in a subsequent RCT and another study on the subject had to be stopped in the face of slow recruitment. Currently, the obstetric scientific community believes that other RCTs are needed before using the pessary in the clinic as a therapeutic option to prevent prematurity in the presence of a short cervix. However, before starting a large RCT, it is important to test the feasibility of recruitment.


Options:
A: Inclusion Criteria:

* Minimal age of 18 years
* Episode of threatened preterm labour

Exclusion Criteria:

* Major fetal abnormalities (requiring surgery or leading to infant death or severe handicap)
* Spontaneous rupture of membranes at the time of randomization
* Cervical cerclage in situ
* Active vaginal bleeding
* Placenta previa

Sample size: 336 singleton (168 per arm) and 128 twins (64 per arm).
B: Inclusion Criteria:

* patient with a short cervix equal to or less than 25 mm by transvaginal ultrasound
* gestational age between 18 (0/7) and 23 (6/7) weeks of gestation according to the results of the ultrasound of the first trimester, or by integrating the date of the last period
* patients who were informed of the study and agreed to sign the consent form.

Exclusion Criteria:

* pregnancy with a fetus with a major congenital malformation - regular and painful uterine activity - history of preterm premature rupture of membranes (PPROM) - active vaginal bleeding - complete and incomplete placenta previa - cerclage of the cervix in place - antecedent of conisation - multiple gestation - ballooning of membranes outside the cervix into the vagina - allergy/intolerance or hypersensitivity to progesterone or any of its ingredients - chronic medical conditions that would interfere with study participation or evaluation of treatment - vaginal administration of another drug.
C: Inclusion Criteria:

* Women with a pregnancy and a history of at least one spontaneous preterm birth before 34+0 weeks and/or a history of late abortion
* 12+0 -18+0 weeks of gestation
* Minimal age of 18 years
* Informed consent signature

Exclusion Criteria:

* The previous preterm delivery is iatrogenic proterm labor
* Major fetal abnormalities (requiring surgery or leading to infant death or severe handicap)
* The pregnant woman with severe cervical erosion, cervical polyp, hemorrhage and the doctors think she could not use cerclage pessary
* The pregnant woman with uterine cervicitis
* The pregnant woman that has been confirmed premature birth
* Cerclage prior to randomisation
* Cerclage prior to randomisation
* Placenta previa totalis
* Active vaginal bleeding at the moment of randomization
* Spontaneous rupture of membranes at the time of randomization
* Silicone allergy
* Painful regular uterine contractions
* The pregnant woman have the indication of operation cervical cerclage
* Current participation in other RCT
D: Inclusion Criteria:

* Diagnosed to be pregnant at up to 24+0 weeks of gestation, with a cervical length measurement of ≤25 mm with a singleton pregnancy, or ≤38 mm in twins pregnancy.
* Does not meet with maternal/fetal/membrane/placental factors detailed in the exclusion criteria.
* Willingness to comply with the protocol for the duration of the study.
* Have signed an informed consent.

Exclusion Criteria:

* Fetal factors: major fetal abnormalities, death of one or both of the fetuses, twins- twin-to-twin transfusion syndrome, and severe growth retardation.
* Maternal factors: prophylactic cervical cerclage in situ, painful regular uterine contractions, active labor, active vaginal bleeding, maternal age under 18, uterine abnormalities (i.e. two cervices), and severe uterine prolapse.
* Membranes and placental factors: placenta previa, ruptured membranes.

Answer: B