Does Hip Extension Prevent Perineal Tears During Birth?

Obstetricians constantly look for simple techniques to reduce perineal lacerations during spontaneous birth. Traditionally, clinicians instruct laboring patients to flex their hips during the expulsive second stage. However, exaggerated hip flexion places substantial mechanical tension on pelvic floor tissues. Therefore, investigators designed a pragmatic clinical trial to test whether hip extension alters tissue trauma at crowning.

Study Design and Hip Extension Protocol

This pragmatic trial randomized 1,206 nulliparous patients delivering singleton term infants. Specifically, care teams guided intervention participants to lower their legs and extend their hips right before crowning. In contrast, patients in the usual care arm maintained standard flexed positioning during delivery. Furthermore, the researchers evaluated a primary composite outcome of significant trauma, spanning second-degree to fourth-degree tears. They also recorded obstetric anal sphincter injuries as a critical secondary outcome.

Key Findings on Perineal Lacerations

Primary intention-to-treat analysis showed no statistically significant difference between groups. In fact, significant tears occurred in 66.6% of the intervention group and 66.2% of the usual care group. Notably, approximately 25% of participants assigned to hip extension did not adhere to the position. Consequently, the authors performed an as-treated analysis to examine compliant patients. In this unadjusted analysis, hip extension showed lower tear rates and reduced anal sphincter injuries. However, these differences lost statistical significance following multivariable adjustment. Nonetheless, ordinal modeling demonstrated a favorable shift toward intact perineal tissues among patients maintaining hip extension.

Clinical Implications for Labor Management

The trial concludes that routine hip extension does not reduce significant perineal tears in intention-to-treat comparisons. Therefore, obstetricians should not mandate hip extension as a definitive protective strategy for all nulliparous deliveries. Instead, delivery teams must prioritize established practices such as controlled crowning and perineal support. Moreover, the substantial nonadherence rate highlights the practical challenge of altering maternal posture during intense crowning sensations. Thus, clinicians should support flexible maternal positioning while maintaining careful vigilance against severe pelvic floor trauma.

Frequently Asked Questions

Q1: Did hip extension lower significant perineal tears in nulliparous births?

No, the intention-to-treat analysis revealed no significant difference in second-degree, third-degree, or fourth-degree tears between groups.

Q2: Why did as-treated analysis show conflicting signals?

Compliant patients initially exhibited fewer tears, but the statistical significance disappeared after adjusting for confounding variables.

Q3: How should obstetricians apply these findings in the labor room?

Obstetricians should allow comfortable maternal positioning rather than forcing rigid posture shifts during delivery.

References

1. Soffer MD et al. Effect of Hip Extension Compared With Usual Positioning on Perineal Lacerations During First Vaginal Delivery: A Randomized Clinical Trial. Obstet Gynecol. 2026 Sep 22. doi: 10.1097/AOG.0000000000006438. PMID: 42771819.
2. American College of Obstetricians and Gynecologists. Prevention and Management of Obstetric Lacerations at Vaginal Delivery. ACOG Practice Bulletin No. 198. Obstet Gynecol. 2018;132(3):e87-e102.
3. Goh R, Goh D, Ellepola H. Perineal tears - A review. Aust Fam Physician. 2018;47(1-2):35-40.