Cerclage for the Reduction of Extreme Preterm Birth in Twin Pregnancies With a Short Cervix or Dilatation

Inclusion Criteria: Women (\> 16 years of age) with a twin pregnancy and: * an asymptomatic short cervix at routine ultrasound investigation (below 24 weeks of gestation) OR * cervical dilatation (below 24 weeks of gestation) Exclusion Criteria: * Women with a mono-amniotic twin pregnancy * Women with twin pregnancy in which one or both children are diagnosed with a major structural, congenital or chromosomal abnormality that is likely to influence the composite adverse neonatal outcome. * Women with dilatation of the cervix and signs of clinical intra-uterine infection, defined by the presence of fever ≥ 38 degrees Celsius. * Women with overt symptoms of preterm labour at time of measurement of short cervix (regular contractions, PPROM, recurrent blood loss). * Women with a placenta previa, defined as a placenta position covering the internal ostium of the cervix. * Women who do not master the Dutch of English language and therefore not able to give written consent