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Oral Plenary Session 1

Oral Plenary Sessions

Oral Plenary Session 1

(5) A Maneuver to Decrease Perineal Lacerations and OASIS: Patient Positioning for Perineal Protection (4P) Study

Wednesday, February 11, 2026

9:00 AM - 9:15 AM

Location: Summit 201 - 204

Submitting Author and Presenting Author(s)

Marti D. Soffer, MD, MPH

Assistant Professor
Department of Obstetrics and Gynecology, MassGeneral Brigham; Division of Maternal-Fetal Medicine; Harvard Medical School
Massachusetts General Hospital, Boston, Massachusetts, United States

Coauthor(s)

KJ

Kaitlyn E. James, MPH, PhD (she/her/hers)

Department of Obstetrics and Gynecology, MassGeneral Brigham; Division of Maternal-Fetal Medicine; Harvard Medical School
Boston, Massachusetts, United States
PL

Pichliya Liang, BS

Department of Obstetrics and Gynecology, MassGeneral Brigham
Massachusetts General Hospital, Boston, Massachusetts, United States
Arlin Delgado, MD (she/her/hers)

Department of Obstetrics and Gynecology, MassGeneral Brigham; Division of Maternal-Fetal Medicine; Harvard Medical School
Boston, Massachusetts, United States
Matthew H. Mossayebi, MD, MPH (he/him/his)

Department of Obstetrics and Gynecology, MassGeneral Brigham; Division of Maternal-Fetal Medicine; Harvard Medical School
Boston, Massachusetts, United States
MH

Margaret Hamp, RN

Department of Obstetrics and Gynecology, MassGeneral Brigham
Massachusetts General Hospital, Boston, Massachusetts, United States
Molly R. Siegel, MD

Massachusetts General Hospital, Division of Maternal Fetal Medicine
Boston, Massachusetts, United States
Mark A. Clapp, MD, MPH (he/him/his)

Physician Investigator
Department of Obstetrics and Gynecology, Mass General Brigham
Boston, Massachusetts, United States
Anjali J. Kaimal, MD, MS (she/her/hers)

Professor and Vice Chair of Clinical Operations, Department of OBGYN
Department of Obstetrics and Gynecology, University of South Florida
Tampa, Florida, United States
WB

William H. Barth, Jr., MD

Department of Obstetrics and Gynecology, MassGeneral Brigham; Division of Maternal-Fetal Medicine; Harvard Medical School
Massachusetts General Hospital, Boston, Massachusetts, United States

Objective:
To determine the effect of hip extension vs usual positioning at the time of crowning on perineal lacerations and obstetrical anal sphincter injury (OASIS).

Study Design:
We conducted a non-blinded RCT of term nulliparous patients with vertex singletons planning vaginal delivery. Once fully dilated, patients were randomized 1:1 to usual care (undirected positioning, typically with hips flexed) or to the intervention (directed hip extension) at crowning/delivery of the head; patients delivered via cesarean were excluded. The primary outcome was significant perineal laceration (SPL), defined as 2^nd, 3^rd, or 4^th degree lacerations. As a prespecified secondary outcome, OASIS was compared between groups. To detect a 10% reduction in SPL, a sample size of 1,206 was needed. Information was collected regarding adherence to the assigned group at delivery. Analysis by intention-to-treat and as-treated was planned a priori.

Results:
1,828 patients were enrolled from 4/2021 to 7/2025. 1,357 were randomized and 1,207 delivered vaginally: 612 in the usual care arm, 595 in the intervention arm. By intention-to-treat, SPL occurred in 66.3% of the usual care and 66.4% of the intervention group (p=0.99) and OASIS occurred in 8.0% and 8.2% respectively (p=0.88) (Table 1). 25.4% of those randomized to the intervention did not deliver with hips extended; longer 2nd stage and operative vaginal delivery were associated with decreased likelihood of receiving the intervention. As-treated analyses demonstrated that the intervention reduced the risk of SPL by 10% (69% vs 62%, p=0.02, RR 0.90 [0.83, 0.98]) and OASIS by 47% (9.9% vs 5.3%, p=0.004, RR 0.53 [0.34, 0.83]) (Table 2). The effect on SPL and OASIS remained after adjustment for birthweight, episiotomy, and time in the 2nd stage.

Conclusion:
Extension of the hips at the time of delivery did not reduce the rates of SPL in the primary analysis; however, 25% assigned to the intervention did not deliver with hips extended. In pre-specified as-treated analysis adjusted for confounders, extension of the hips at the time of delivery was associated with reduced SPL and OASIS.