Impact of Pelvic Rest Recommendations on Follow-Up and Resolution of Placenta Previa and Low-Lying Placenta.

OBJECTIVE: To determine the rate of resolution of placenta previa and low-lying placenta (LLP) and the effect of pelvic rest recommendations on the timing of follow-up imaging.

METHODS: Retrospective review of pregnancies with previa/LLP detected on mid-trimester exam at our ultrasound unit from 2019 to 2021. LLP was defined as the lower edge of placenta located within 2 cm of the internal cervical os. Previa was defined as any portion of the placenta touching with the internal os. Demographics, placental location, activity restrictions, and delivery outcomes were analyzed. Timing of follow-up imaging was stratified by individuals advised and not advised pelvic rest.

RESULTS: Exactly 144 patients had previa and 266 had LLP on the mid-trimester exam with complete records. Previa resolution happened in 51.4% (74/144) of cases. Exactly 62% (46/74) of previa resolutions occurred by the 28-week ultrasound. Exactly 45% (65/144) of previa patients were advised pelvic rest. Most pelvic rest and non-pelvic rest patients had a 28-week scan. Even when clearance occurred, most patients in both groups had a repeat ultrasound at 32 weeks. Exactly 75% of LLP resolved by the 28-week scan, and the remainder by delivery. Exactly 12% (32/259) of LLP patients were advised pelvic rest.

CONCLUSION: Most societies recommend follow-up imaging at 32 weeks; however, our results suggest this may be done sooner and closer to 28 weeks. Pelvic rest did not affect timing of repeat imaging or delivery.