The prevalence of short cervix between 20 and 24 weeks of gestation and vaginal progesterone for prolonging of gestation.

OBJECTIVE: The objective of this study is to understand the prevalence of short cervical length between 20 and 24 weeks gestation in China and to evaluate the efficacy of micronized progesterone for prolonging gestation in nulliparous patients with a short cervix.

METHODS: From May 2010 to May 2015, a total of 25 328 asymptomatic women with singleton pregnancies at Peking University First Hospital had their cervical length routinely measured between 20 and 24 weeks of gestation. A cervical length of 25 mm or less was defined as a shortened cervical length. The therapies prescribed include vaginal micronized progesterone capsules (200 mg each night) or bed rest from 20 to 34 weeks of gestation. The primary outcome was spontaneous delivery before 33 weeks.

RESULTS: (1) One hundred fourteen women had a cervical length of ≤25 mm (0.45%). (2) Twenty-nine of which with previous spontaneous preterm delivery or late pregnancy loss had cervical cerclage, the remaining 85 women by the use of vaginal progesterone or simply resting activity restriction to prevent preterm birth. (3) In 85 nulliparous women treated by progesterone or bed rest, progesterone use in cervical length between 10 and 20 mm was associated with a statistically significant reduction in the incidence of preterm birth at <33 weeks of gestation (9.5% versus 45.5%, p = 0.02) compared with bed rest. There were no significant differences in cervical length between 20 and 25 mm in their rates of spontaneous preterm delivery at <33 (5.3% versus 3.2%, p = 0.72), <37 (33.3% versus 54.5%, p = 0.25), or <35 weeks (14.3% versus 45.5, p = 0.06) of gestation between vaginal progesterone and bed rest.

CONCLUSION: The rate of short cervical length was less than expected. Vaginal progesterone is efficacious for the prolonging of gestation in women with a cervical length of 10-20 mm in the mid-trimester for a singleton gestation and nulliparous women. For a cervical length of 20-25 mm in the mid trimester, vaginal progesterone compared with bed rest did not prolong pregnancy.