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Prematurity

Poster Session 2

(531) Establishing risk thresholds for asymptomatic cervical lengths in twin pregnancies.

Tuesday, February 13, 2024
3:30 PM – 5:00 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Foundation Awardee
Objective:

In singleton gestations, a mid-trimester cervical length (CL) < 25mm (< 10th percentile) is a risk factor for spontaneous preterm birth (sPTB). This threshold unlocks interventions to reduce this risk. Currently, the same threshold is used to trigger interventions for twin gestations, however there is a paucity of data to guide whether the same CL thresholds should be used in twin gestations. We aim to determine a CL threshold of concern for sPTB among twins, as well as the optimal time for transvaginal assessment.


Study Design:

This is a retrospective cohort study at an academic medical center reviewing all twin pregnancies over a 5-year period where an asymptomatic mid-trimester transvaginal CL was available. All CL were performed by Registered Diagnostic Medical Sonographers at a single site. The mean CL was calculated at various points between 15-28 weeks’ gestation among patients who had a sPTB (defined as preterm labor or PPROM leading to sPTB before 37 weeks) and patients who did not have a sPTB. T-tests compared the means at each time point to determine if there was a gestational age among patients with sPTB where there was a deviation in mean CL.


Results:

179 twin gestations with at least one documented asymptomatic mid-trimester CL were available. Table 1 shows the mean CL at various gestational ages for all patients, those with a sPTB, and those without a sPTB. Differences in CL are noted beginning at 23 weeks and are most pronounced between 26 and 28 weeks with the mean CL in the sPTB group being 29.7±11.6mm compared to 36.8±10.3mm in those without sPTB (p=0.004). Importantly, the mean CL among twin gestations with a sPTB remained above the 25mm risk threshold, and often above 30mm prior to 26 weeks.


Conclusion:

In twin pregnancies, a higher CL threshold may be considered when determining those at higher risk of sPTB. Larger studies are needed to validate these findings, which may lead to consideration of interventions to prevent sPTB in twin pregnancies at a longer CL. Additionally, there may be limited value for CL as a risk assessment before 21 weeks in twins.