Berghella V, Roman A Cerclage in twins: we can do better! Am J Obstet Gynecol. 2014 Jul;211(1):5-6. doi: 10.1016/j.ajog.2014.03.037.
Conde-Agudelo A, Romero R, Hassan SS, Yeo L Transvaginal sonographic cervical length for the prediction of spontaneous preterm birth in twin pregnancies: a systematic review and metaanalysis. Am J Obstet Gynecol. 2010 Aug;203(2):128.e1-12. doi: 10.1016/j.ajog.2010.02.064. Epub 2010 Jun 23. Review.
Miller ES, Rajan PV, Grobman WA Outcomes after physical examination-indicated cerclage in twin gestations. Am J Obstet Gynecol. 2014 Jul;211(1):46.e1-5. doi: 10.1016/j.ajog.2014.03.034. Epub 2014 Mar 18.
Rebarber A, Bender S, Silverstein M, Saltzman DH, Klauser CK, Fox NS Outcomes of emergency or physical examination-indicated cerclage in twin pregnancies compared to singleton pregnancies. Eur J Obstet Gynecol Reprod Biol. 2014 Feb;173:43-7. doi: 10.1016/j.ejogrb.2013.11.016. Epub 2013 Nov 28.
Saccone G, Rust O, Althuisius S, Roman A, Berghella V Cerclage for short cervix in twin pregnancies: systematic review and meta-analysis of randomized trials using individual patient-level data. Acta Obstet Gynecol Scand. 2015 Apr;94(4):352-8. doi: 10.1111/aogs.12600. Epub 2015 Mar 1. Review.
Interventional studies are often prospective and are specifically tailored to evaluate direct impacts of treatment or preventive measures on disease.
Observational studies are often retrospective and are used to assess potential causation in exposure-outcome relationships and therefore influence preventive methods.
Expanded access is a means by which manufacturers make investigational new drugs available, under certain circumstances, to treat a patient(s) with a serious disease or condition who cannot participate in a controlled clinical trial.
Clinical trials are conducted in a series of steps, called phases - each phase is designed to answer a separate research question.
Phase 1: Researchers test a new drug or treatment in a small group of people for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.
Phase 2: The drug or treatment is given to a larger group of people to see if it is effective and to further evaluate its safety.
Phase 3: The drug or treatment is given to large groups of people to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the drug or treatment to be used safely.
Phase 4: Studies are done after the drug or treatment has been marketed to gather information on the drug's effect in various populations and any side effects associated with long-term use.