Progesterone and Cervical Pessary in Twins

Inclusion Criteria: * Twin pregnancy ( dichorionic or monochorionic diamniotic) * Both fetuses alive * Asymptomatic short cervix according to gestational age ( measurement less or equal 30 mm between 16 weeks + 0 day and 22 weeks + 0 day, less or equal 25 mm between 22 weeks + 1 day and 24 weeks + 0 day and less or equal 20 mm between 24 weeks + 1 day and 27 weeks + 6 days) * Gestational age between 16 to 27weeks and 6 days * Intact membranes * Informed consent Exclusion Criteria: * Monoamniotic twins * Twin Twin transfusion syndrome * Rupture membranes * Major malformation or chromosomal abnormality at least one fetus * Women with Cervical cerclage in the current pregnancy * Ballooning of membranes outside the cervix into the vagina * Placenta previa * Treatment with progesterone before randomization * Allergy of the excipientes of the micronized progesterone * Labor * Severe hepatic disfunction, porphyria, otosclerosis, severe depression * Use of drugs that interfere the effects of progesterone