Please select the eligibility criteria that correspond to the clinical trial below.
Title: Prevention of Preterm Birth in Pregnant Women at Risk Identified by Ultrasound: Evaluation of Two Treatment Strategies
Brief Summary: The preterm birth is considered as a main problem in the modern obstetrics, being the responsible of greatest of 50% neonatal morbimortality and heavy costs. Despite the significant medical advances, the rate of prematurity has not declined over the past 40 years and even continues to rise in the developed countries. In order to decrease the prematurity is necessary that two premises: to identify the pregnant women at risk of preterm birth, and dispose of useful measures aimed at prolonging the pregnancy and therefore avoid preterm delivery. The investigators propose a clinical trial with the objective to identify effective strategies to reduce the premature birth (34 weeks and earlier) rate in the population of pregnant women at risk for premature birth, which will be identified by ultrasound during the second trimester of their pregnancy.

The investigators intend to compare two accepted strategies: administration of progesterone (vaginally) or the placement of vaginal pessaries. These 2 strategies are affordable, easy to apply, and they present very few maternal-fetal secondary effects.


Options:
A: Inclusion Criteria:

* 18-50 years of age
* Singleton pregnancy (limits the participants to female gender)
* Short cervical length (less than or equal to 25 mm) on second trimester ultrasound at 18-23 6/7 weeks gestation

Exclusion Criteria:

* Multiple gestation
* Prior spontaneous preterm birth 16-36 6/7 weeks
* Ruptured membranes
* Lethal fetal structural anomaly
* Fetal chromosomal abnormality
* Cerclage in place (or planned placement)
* Vaginal bleeding
* Suspicion of chorioamnionitis
* Ballooning of membranes outside the cervix into the vagina or CL = 0 mm on transvaginal ultrasound
* Painful regular uterine contractions
* Placenta previa
B: Inclusion Criteria:

* Pregnant women with short cervix (=\< 25 mm) identified by use of routine transvaginal ultrasonography at 19-22 weeks of gestation.
* Single pregnancy
* Women older than 18 year-old
* Women sign informed consent according GCP and local legislation
* Gestational age at randomization between 20+1 and 23+6 weeks.

Exclusion Criteria:

* Major fetal abnormalities
* Major uterine abnormalities
* Placenta praevia during current pregnancy
* Vaginal bleeding or ruptured membranes in the moment of randomization
* Cervical cerclage in situ
* History of cone biopsy
* Allergic to peanuts
* Contraindication for Progesterone usage.
* Active treatment with Progesterone at randomization.
* History of 3 or more premature labor.
* If in the investigator's opinion, there are findings on physical examination, abnormalities in the results of clinical analyzes or other medical factors, social or psycho-social that could negatively influence.
* Women unable to give the informed consent
C: 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.
D: Inclusion Criteria:

1. Short cervical length equal or less than 20 mm
2. Singleton pregnant women between 18 -24 weeks with no prior history of preterm deliveries.
3. 18 years or older at the time of enrollment.
4. Consent to participate in the study

Exclusion Criteria:

1. Previous preterm delivery less than 37 weeks
2. Major fetal anomalies
3. Multiple pregnancy
4. Patient currently with cervical cerclage in-situ for the treatment of incompetence cervix.
5. Regular uterine contractions or significantly dilated cervical canal
6. Age less than 18 years
7. Decline to participate in the study

Answer: B