Up to ¼ of premature births in the second trimester are due to an insufficient or short cervix , which means that a significant number of preterm births could be prevented with proper care. During prenatal care, pregnant women should have their cervixes measured between about 19-24 weeks. If the OB/GYN finds that the cervix is short, the OB/GYN should consider placing their mother on progesterone. This hormone helps prolong pregnancy and prevent preterm labor with single pregnancies.
Usually (when a mother has a history of prior preterm birth), OB/GYNs begin progesterone therapy around 16-20 weeks until about 36 weeks. This is done via weekly intramuscular injection. If a woman has a shortened cervix without a prior history of preterm birth, progesterone is administered vaginally beginning around 18 weeks. This is something typically done in conjunction with a cervical cerclage to maximize the chances of prolonging a pregnancy to a sufficient length.
- Conde-Agudelo, A et al. Vaginal Progesterone to Prevent Preterm Birth in Pregnant Women with a Sonographic Short Cervix: Clinical and Public Health Implications. Am J Obstet Gynecol. 2016 Feb;214(2):235-42. doi: 10.1016/j.ajog.2015.09.102. Epub 2015 Oct 9.
- Coomarasamy A et al. A Randomized Trial of Progesterone in Women with Recurrent Miscarriages. N Engl J Med 2015; 373:2141-2148. November 26, 2015. DOI: 10.1056/NEJMoa1504927.
- Kumar, D. et al. Progesterone Inhibits In Vitro Fetal Membrane Weakening. Am J Obstet Gynecol. 2015 Oct;213(4):520.e1-9. doi: 10.1016/j.ajog.2015.06.014. Epub 2015 Jun 10.