Clinician-to-Clinician Update Clinician-to-Clinician Update

The Management of Short Cervical Length

November 2014 - Maternal Fetal Medicine

Approximately 1 in 8 infants born in the United States is born preterm, or prior to 37 weeks of gestation, and preterm birth accounts for the vast majority of neonatal morbidity and mortality.1 Although the etiology of preterm birth is multifactorial, it has been well documented that decreasing cervical length is associated with an increased risk for preterm birth.2, 3

Patient

A 25-year-old primigravida was evaluated at 21 weeks 4 days gestation for routine obstetric ultrasound imaging. Transabdominal imaging of the cervix suggested cervical funneling with a shortened cervical length (Figure 1). Transvaginal ultrasonography was then performed, which also demonstrated funneling with a shortened residual length of 1.45 cm (Figure 2). The patient denied contractions. 

figure-1-443x290
— Figure 1. Uterine cervix imaged by transabdominal ultrasound
figure-2-443x303
— Figure 2. Uterine cervix imaged by transvaginal ultrasound

Management

Speculum and digital examinations were performed, which demonstrated a closed cervix. The decision was made to initiate therapy with vaginal micronized progesterone (200 mg) every evening through 36 weeks 6 days of gestation. Activity modification was not recommended. A follow-up transvaginal ultrasound was scheduled for the following week. At that time, there was no evidence of further cervical shortening or dilation, and the patient was advised to continue the vaginal progesterone. The patient ultimately delivered at 38 weeks of gestation.

Discussion

At this time there is no consensus on universal cervical length screening for the population of pregnant women at low risk for preterm birth. However, shortened cervical length is typically seen between 18-22 weeks of gestation, making this is a reasonable time period to screen. Given that patients with shortened cervical length are at a higher risk for preterm birth, several interventions have been studied for their effectiveness in reducing the preterm birth rate. Activity restriction is not routinely recommended, as it has not been shown to be of benefit in reducing the risk of preterm birth. 4 Surgical cervical cerclage does not appear to be beneficial in reducing the risk of preterm birth for ultrasonographically detected cervical shortening in the low risk population.5 Vaginal progesterone has been demonstrated to reduce the risk of preterm birth by approximately 45% in otherwise low-risk women with cervical length < 20 mm prior to or at 24 weeks of gestation.6, 7 Vaginal progesterone can be administered every evening either as 200 mg of micronized progesterone or 90 mg of progesterone gel.

References

1. Goldenberg RL, Culhane JF, Iams JD, Romero R. Epidemiology and causes of preterm birth. Lancet. 2008;371:75-84.

2. Iams JD, Goldenberg RL, Meis PJ, et al. The length of the cervix and the risk of spontaneous premature delivery. N Engl J Med. 1996;334:567-573.

3. Crane JM, Hutchens D. Transvaginal sonographic measurement of cervical length to predict preterm birth in asymptomatic women at increased risk: a systematic review. Ultrasound Obstet Gynecol. 2008;31:579-87.

4. Grobman WA, Gilbert SA, Iams JD, et al. Activity restriction among women with a short cervix. Obstet Gynecol. 2013;121:1181-6.

5. To MS, Alfirevic Z, Heath VC, et al. Cervical cerclage for prevention of preterm delivery in women with short cervix: randomized controlled trial. Lancet. 2004;363:1849-53.

6. Hassan SS, Romero R, Vidyadhari D, et al. Vaginal progesterone reduces the rate of preterm birth in women with a sonographic short cervix: a multicenter, randomized, double-blind, placebocontrolled trial. Ultrasound Obstet Gynecol. 2011;38:18-31.

7. Fonseca EB, Celik E, Parra M, et al. Progesterone and the risk of preterm birth among women with a short cervix. Fetal Medicine Foundation Second Trimester Screening Group. N Engl J Med. 2007;357:462-9.

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