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Ultrasound/Imaging

Poster Session 4

(1039) Resolution of low lying placentas: Does the distance matter?

Wednesday, February 14, 2024
1:00 PM – 2:30 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective: Most pregnant women undergo a 2nd-trimester transvaginal ultrasound (US) that often includes a trans-vaginal scan to determine cervical length and placental location relative to the cervix. A low-lying placenta (edge measuring ≤2cm from the cervix) is a frequent finding. Although most low-lying placentas will resolve by term, there is limited information on whether the distance from the cervical os at time of diagnosis affects time to resolution. The objective of this study was to test the hypothesis that the distance from the edge of a low-lying placenta to the cervical os at time of diagnosis is inversely correlated with the time to resolution: the shorter the distance, the longer it takes for the low-lying placenta to resolve.

Study Design: IRB approved retrospective cohort study of singleton pregnancies who had a transvaginal US between 16-0/7-24-0/7 weeks gestation from 1/2019-12/2022. Subjects were identified by querying the US database for ICD-10 code O44.42. Patients were included if they had follow-up transvaginal scans until resolution (placental edge >2cm from the cervix) or within 4 weeks of delivery. Patients were excluded if their low lying placenta resolved before 20 weeks. Statistical analysis included Pearson correlation.

Results: 626 patients were identified, of which 350 patients met inclusion criteria. Three (3) patients had an unresolved low lying placenta by time of delivery, leaving 347 patients with a resolved low lying placenta (99.14%). The mean (± SD) gestational age at diagnosis was 20-3/7 (±1-5/7) weeks, and the mean (±SD) time to resolution was 6-3/7 (± 3-2/7) weeks. The mean distance (±SD) of the placental edge from the cervical os at diagnosis was 9.6mm (±6.4mm), with a median distance of 11mm [range 0-20mm]. Pearson correlation showed no correlation between the distance and time to resolution (r = -0.027, p=0.616).

Conclusion: The vast majority of low lying placentas will resolve by time of delivery, but the distance from the placental edge to the cervical os at time of diagnosis does not impact time to resolution.