Review Question - QID 105364

Transvaginal ultrasound is the study of choice for evaluating cervical incompetence or insufficiency. A cervical length appearing less than 2.5 cm on pelvic exam at 23-28 weeks gestation is concerning for potential cervical insufficiency and warrants further investigation.

Cervical length at or around 24 weeks gestation is an indicator of the potential risk of preterm birth, with shorter cervical lengths demonstrating an association with increasing frequency of spontaneous preterm delivery. The cervical length is expected to shorten as pregnancy progresses; a short cervix is defined as cervical length less than the 10th percentile for gestational age. Normal cervical length outside of pregnancy is 4 to 5 cm. Past history of prior cervical dilation or cervical excision procedures (such as LEEP or conization) increases the likelihood of cervical incompetence and therefore of preterm birth.

Ressel et al. review the ACOG guidelines regarding diagnosis and management of cervical insufficiency. If a short cervix is identified at a gestational age at or after the age of fetal viability, then workup should include the following: ultrasound to assess for fetal anomalies, tocometry to monitor for contractions, and clinical exclusion of chorioamnionitis. Before 20 weeks gestation, it is difficult to adequately distinguish cervix from lower uterine segment on ultrasound.

Berghella et al. investigate the role of cervical assessment by ultrasound for the prevention of pre-term birth. They conclude that there is insufficient evidence to recommend routine screening of symptomatic or asymptomatic pregnant patients with transvaginal ultrasound for evaluation of cervical length.

Illustration A shows a visual representation of a short cervix.
Illustration B shows cervical length and associated percentiles by gestational age; note that the 10th percentile correlates to less than 25 mm at 39 weeks gestation.

Incorrect Answers:
Answer 1: The position of the cervix has not been shown to be correlated with increased incidence of adverse obstetric outcomes and does not warrant further investigation.
Answer 3: Breech positioning does not warrant further investigation at such an early gestational age.
Answer 4: Shortened, not lengthened, cervical length is concerning for cervical insufficiency and warrants further confirmation with transvaginal ultrasound imaging.
Answer 5: The position of the cervix has not been shown to be correlated with increased incidence of adverse obstetric outcomes and does not warrant further investigation. However, anterior positioning of the cervix is indicative of increased ripeness of the cervix for labor or induction.