Approach to transvaginal sonographic screening of cervical length in singleton pregnancy and management of pregnant people with a short cervix

The management of pregnant people with a singleton pregnancy, no prior spontaneous preterm birth, and a short cervix varies among providers. Some offer cerclage when the cervix is very short (eg, <10 or 15 mm). When the cervix is ≤25 mm, we suggest that clinicians discuss the available data and its limitations with the patient and make a shared decision regarding placement of a cerclage. Refer to UpToDate content on second-trimester evaluation of cervical length for prediction of spontaneous preterm birth.

The best approach to pregnant people with a prior spontaneous twin birth is also controversial. Some studies have reported that a prior spontaneous twin birth is associated with an increased risk of spontaneous preterm birth in the subsequent singleton pregnancy. The increased risk appears to be limited to previous twin births <34 weeks. Therefore, if the prior twin preterm birth was ≥34 weeks, we manage the subsequent singleton pregnancy the same as in patients with no prior preterm spontaneous birth. If <34 weeks, we offer progesterone supplementation and monitor cervical length, as described for singletons. This is the author's approach to monitoring cervical length and management of pregnant people with a short cervix. This remains a controversial area, and variations of this approach exist worldwide.