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[ Home ](https://mdster.com) 2. [ Blog ](https://mdster.com/blog) 3. [ Case Discussion ](https://mdster.com/blog?category=case-discussion) 4. Low Operative Vaginal Delivery: Vacuum, Forceps, and OASIS Repair [ Case Discussion ](https://mdster.com/blog?category=case-discussion) Low Operative Vaginal Delivery: Vacuum, Forceps, and OASIS Repair =================================================================== A board-focused case discussion on assisted vaginal birth, pelvic assessment, neonatal scalp injury, and third-degree tear repair. [ MDster Editorial Team ](https://mdster.com/about) · May 29, 2026 · 5 min read · 124 [ Reviewed by Dr. Ali Ragab, MBBCH, MSc, MCAI ](https://mdster.com/medical-reviewers/dr-ali-ragab) [Editorial Policy](https://mdster.com/editorial-policy) | [Corrections Policy](https://mdster.com/corrections) [ Obstetrics & Gynecology ](https://mdster.com/blog?tag=obstetrics-gynecology) [ Operative Vaginal Delivery ](https://mdster.com/blog?tag=operative-vaginal-delivery) [ Labor Management ](https://mdster.com/blog?tag=labor-management) [ Vacuum Extraction ](https://mdster.com/blog?tag=vacuum-extraction) [ Forceps Delivery ](https://mdster.com/blog?tag=forceps-delivery) [ OASIS ](https://mdster.com/blog?tag=oasis) ![Low Operative Vaginal Delivery: Vacuum, Forceps, and OASIS Repair](https://mdster.com/storage/blog/images/low-operative-vaginal-delivery-vacuum-forceps-and-oasis-repair.jpg) Share this article Share this post On this page 1. [ Naming the Procedure Correctly ](#naming-the-procedure-correctly) 2. [ The Second-Stage Differential ](#the-second-stage-differential) 3. [ Prerequisites Before Instrument Application ](#prerequisites-before-instrument-application) 4. [ Vacuum Versus Forceps: Choosing the Harm Profile ](#vacuum-versus-forceps-choosing-the-harm-profile) 5. [ Vacuum Failure and Neonatal Scalp Swelling ](#vacuum-failure-and-neonatal-scalp-swelling) 6. [ If Forceps Leads to 3c OASIS ](#if-forceps-leads-to-3c-oasis) 7. [ Clinical Application ](#clinical-application) 8. [ Key Points for Board Exams ](#key-points-for-board-exams) 9. [ Conclusion ](#conclusion) 10. [ Frequently Asked Questions ](#blog-faqs) 11. [ References ](#references-heading) On this page 1. [ Naming the Procedure Correctly ](#naming-the-procedure-correctly) 2. [ The Second-Stage Differential ](#the-second-stage-differential) 3. [ Prerequisites Before Instrument Application ](#prerequisites-before-instrument-application) 4. [ Vacuum Versus Forceps: Choosing the Harm Profile ](#vacuum-versus-forceps-choosing-the-harm-profile) 5. [ Vacuum Failure and Neonatal Scalp Swelling ](#vacuum-failure-and-neonatal-scalp-swelling) 6. [ If Forceps Leads to 3c OASIS ](#if-forceps-leads-to-3c-oasis) 7. [ Clinical Application ](#clinical-application) 8. [ Key Points for Board Exams ](#key-points-for-board-exams) 9. [ Conclusion ](#conclusion) 10. [ Frequently Asked Questions ](#blog-faqs) 11. [ References ](#references-heading) At 39 weeks, a nulliparous patient has pushed for 3 hours with a functioning epidural. The tracing remains reassuring overall, but intermittent variable decelerations are appearing, and she is exhausted. The head is OA, +2 station, ≤1/5 palpable abdominally, and not visible at the introitus without separating the labia. Naming the Procedure Correctly ------------------------------ This is a **low operative vaginal delivery**, not an outlet delivery. The leading bony point is at +2 cm station, but the skull has not reached the pelvic floor and is not visible at the introitus without labial separation. ClassificationKey findingOutletScalp visible, skull on pelvic floorLowLeading point at +2 cm or lower, not on pelvic floorMidpelvicEngaged head above +2 cm The OA position and absent asynclitism make this a favorable nonrotational case. The harder question is not “Can I pull?” but “Have I excluded the reasons this will fail?” The Second-Stage Differential ----------------------------- The differential for delayed descent is narrow but consequential: - Maternal exhaustion with otherwise adequate mechanics - Occult malposition, especially OP or transverse position - Midpelvic contraction or cephalopelvic disproportion - Ineffective expulsive effort despite contractions - Dense neuraxial block limiting coordinated pushing - Full bladder, now corrected in this case The midpelvis is the key anatomic checkpoint. The interspinous diameter at the ischial spines represents the clinically important “least pelvic dimensions,” and arrest here should make the operator pause before committing to traction. Prerequisites Before Instrument Application ------------------------------------------- Before cup or blades, the operator should confirm: - Fully dilated cervix - Ruptured membranes - Empty bladder - Exact fetal position and degree of rotation - Adequate analgesia and maternal cooperation - No suspected fetal bleeding disorder or bone demineralization, particularly for vacuum - Informed consent covering failed attempt and cesarean backup - Experienced operator, appropriate instrument, and neonatal support available > **Clinical Pearl:** A low station does not rescue poor judgment. If position is uncertain, use intrapartum ultrasound rather than applying an instrument to a presumed OA head. Vacuum Versus Forceps: Choosing the Harm Profile ------------------------------------------------ In this case, both vacuum and forceps are plausible. Clinical judgment dictates the choice, based on operator skill, urgency, fetal considerations, and maternal pelvic floor risk. InstrumentMaternal tradeoffFetal tradeoffVacuumLess maternal soft-tissue trauma than forcepsMore cephalohematoma, subgaleal hemorrhage, retinal hemorrhageForcepsMore vaginal trauma and OASIS riskMore facial nerve injury, corneal abrasion, rare skull injury Vacuum is attractive for an OA low delivery when delivery is not immediately emergent. Conversely, forceps may be preferred when more controlled delivery is needed or when vacuum is contraindicated. Absolute contraindications to vacuum include fetal bleeding disorders, significant bone demineralization disorders, and gestational ages where vacuum is considered unsafe by local policy. Face presentation is also not appropriate for vacuum extraction. Vacuum Failure and Neonatal Scalp Swelling ------------------------------------------ A vacuum attempt should show descent with traction. If there is no progressive descent, repeated cup detachments, or concern that traction is becoming excessive, the safest move is to stop and proceed to cesarean or another appropriate plan. Sequential instruments increase trauma risk and should not be casual. After difficult vacuum delivery, a fluctuant scalp swelling demands urgent distinction: FindingCephalohematomaSubgaleal hemorrhagePlaneSubperiostealBeneath galea aponeuroticaSuturesDoes not crossCrosses sutures widelyRiskJaundice, anemiaHypovolemic shock, death if missed Subgaleal hemorrhage results from emissary vein rupture into a large potential space. The clue is progressive, diffuse, boggy swelling with pallor, tachycardia, hypotonia, or falling hematocrit. If Forceps Leads to 3c OASIS ---------------------------- A 3c tear means both EAS and IAS are torn, with rectal mucosa intact. The repair should occur in an operating room or equivalent setting with good lighting, anesthesia, instruments, and assistance. Repair sequence: 1. Inspect rectal mucosa with digital rectal examination. 2. Repair rectal mucosa first if a fourth-degree extension is found. 3. Identify and repair IAS separately with delayed absorbable suture. 4. Repair EAS using end-to-end or overlap technique for full-thickness disruption. 5. Reapproximate perineal muscles and vaginal mucosa anatomically. 6. Perform a final rectal examination to exclude transrectal sutures. For EAS, both end-to-end and overlap repairs are acceptable for full-thickness injury. Partial-thickness EAS injury is generally repaired end-to-end. Post-repair care should include broad-spectrum antibiotics, stool softening or laxative regimen, analgesia, pelvic floor follow-up, and clear counseling about wound symptoms and continence changes. Clinical Application -------------------- In the vignette, the best answer is not “vacuum” or “forceps” in isolation. The safest answer is a low, nonrotational operative vaginal delivery only after confirming prerequisites, counseling the patient, preparing for abandonment, and choosing the instrument whose risks fit the clinical moment. Key Points for Board Exams -------------------------- - +2 station, OA, not on pelvic floor equals **low operative vaginal delivery**. - Outlet delivery requires scalp visible without separating the labia and skull on the pelvic floor. - The midpelvis, especially the interspinous diameter, is the classic arrest point. - Vacuum has more scalp and extracranial bleeding risk; forceps has more maternal soft-tissue and OASIS risk. - Subgaleal hemorrhage crosses sutures and can cause shock. - A 3c tear involves EAS and IAS, but not rectal mucosa. - Broad-spectrum antibiotics after OASIS repair reduce infectious morbidity. Conclusion ---------- Operative vaginal delivery is a physiologic and anatomic decision, not merely a station-based permission slip. In a low OA case with maternal exhaustion and emerging variables, assisted birth may be appropriate, but only if the operator can articulate the classification, prerequisites, instrument-specific risks, failure plan, and OASIS repair strategy. Frequently Asked Questions ---------------------------- ### Why is this not classified as an outlet operative vaginal delivery? Because the skull is not on the pelvic floor and is not visible at the introitus without separating the labia. At +2 station, this is low operative vaginal delivery. ### When should vacuum be avoided in an otherwise favorable low OA delivery? Avoid vacuum with suspected fetal bleeding disorder, significant bone demineralization, unsafe gestational age by policy, or an unsuitable presentation such as face presentation. ### What neonatal finding most strongly suggests subgaleal hemorrhage? Diffuse, fluctuant scalp swelling that crosses suture lines, especially if progressive or associated with pallor, tachycardia, hypotonia, or anemia. ### What structures are torn in a 3c perineal laceration? A 3c tear involves both the external and internal anal sphincters. Rectal mucosal involvement would make it a fourth-degree tear. References (4) ------------------ 1. 1. [ ACOG Practice Bulletin No. 219: Operative Vaginal Birth. Obstet Gynecol. 2020. ](https://pubmed.ncbi.nlm.nih.gov/32217976/) 2. 2. [ RCOG Green-top Guideline No. 26: Assisted Vaginal Birth. 2020. ](https://www.rcog.org.uk/guidance/browse-all-guidance/green-top-guidelines/assisted-vaginal-birth-green-top-guideline-no-26/) 3. 3. [ RCOG Green-top Guideline No. 29: Management of Third- and Fourth-Degree Perineal Tears. 2015. ](https://www.rcog.org.uk/guidance/browse-all-guidance/green-top-guidelines/third-and-fourth-degree-perineal-tears-management-green-top-guideline-no-29/) 4. 4. [ ACOG Practice Bulletin No. 198: Prevention and Management of Obstetric Lacerations at Vaginal Delivery. 2018. ](https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2018/09/prevention-and-management-of-obstetric-lacerations-at-vaginal-delivery) Keep going Build confidence in OB/GYN with focused practice -------------------------------------------------- - Labor & delivery + postpartum essentials - Gynecology, screening, and common procedures - Review weak topics and improve faster [ Start practicing ](https://mdster.com/user/dashboard) [ Explore Obstetrics & Gynecology ](https://mdster.com/speciality/obstetrics-gynecology) [ View pricing ](https://mdster.com/pricing) [ Explore features ](https://mdster.com/features) No credit card required. Full access to all features\*. No commitment. Cancel anytime. \*AI SOE Examiner is limited to 10 cases monthly for Advanced & Bundle subscribers. Explore topics: [ # Obstetrics & Gynecology ](https://mdster.com/blog?tag=obstetrics-gynecology) [ # Operative Vaginal Delivery ](https://mdster.com/blog?tag=operative-vaginal-delivery) [ # Labor Management ](https://mdster.com/blog?tag=labor-management) [ # Vacuum Extraction ](https://mdster.com/blog?tag=vacuum-extraction) [ # Forceps Delivery ](https://mdster.com/blog?tag=forceps-delivery) [ # OASIS ](https://mdster.com/blog?tag=oasis) [ Back to all posts ](https://mdster.com/blog) Discussion () ----------------- Join the discussion [ Log in ](https://mdster.com/auth/login) or [ Sign up ](https://mdster.com/auth/register) No comments yet Be the first to share your thoughts! ![]() More in Case Discussion ----------------------- [ See all ](https://mdster.com/blog?category=case-discussion) [### Placental Abruption After Minor Trauma: A 34-Week Case Discussion 8 min read Jul 12, 2026 ](https://mdster.com/blog/placental-abruption-after-minor-trauma-a-34-week-case-discussion) [### Withdrawal of Life Support in Septic Shock: ICU Case Discussion 7 min read Jul 10, 2026 ](https://mdster.com/blog/withdrawal-of-life-support-in-septic-shock-icu-case-discussion) [### Septic Shock RSI and CICO: A Difficult Airway Case Discussion 6 min read Jul 09, 2026 ](https://mdster.com/blog/septic-shock-rsi-and-cico-a-difficult-airway-case-discussion) Related Posts ------------- [ ![Placental Abruption After Minor Trauma: A 34-Week Case Discussion](https://mdster.com/storage/blog/images/placental-abruption-after-minor-trauma-a-34-week-case-discussion.jpg) Case Discussion ### Placental Abruption After Minor Trauma: A 34-Week Case Discussion A board-focused case discussion on evaluating minor blunt trauma at 34 weeks, recognizing placental abruption, timing fetal monitoring, and dosing Rh immune globulin. 8 min read 0 comments ](https://mdster.com/blog/placental-abruption-after-minor-trauma-a-34-week-case-discussion) [ ![Withdrawal of Life Support in Septic Shock: ICU Case Discussion](https://mdster.com/storage/blog/images/withdrawal-of-life-support-in-septic-shock-icu-case-discussion.jpg) Case Discussion ### Withdrawal of Life Support in Septic Shock: ICU Case Discussion A board-style ICU case on refractory septic shock, surrogate ethics, terminal extubation, symptom control, prognosis after withdrawal, and high-yield documentation points. 7 min read 0 comments ](https://mdster.com/blog/withdrawal-of-life-support-in-septic-shock-icu-case-discussion) [ ![Embryology Lab Concepts for Clinicians in IVF and ICSI](https://mdster.com/storage/blog/images/embryology-lab-concepts-for-clinicians-in-ivf-and-icsi.jpg) Medical Education ### Embryology Lab Concepts for Clinicians in IVF and ICSI A high-yield clinician’s guide to embryology lab language in IVF/ICSI: fertilization checks, embryo grading, blastocyst culture, vitrification, and male-factor ICSI. 6 min read 0 comments ](https://mdster.com/blog/embryology-lab-concepts-for-clinicians-in-ivf-and-icsi) [ ![Septic Shock RSI and CICO: A Difficult Airway Case Discussion](https://mdster.com/storage/blog/images/septic-shock-rsi-and-cico-a-difficult-airway-case-discussion.jpg) Case Discussion ### Septic Shock RSI and CICO: A Difficult Airway Case Discussion A board-style anesthesiology case on septic shock, RSI, failed intubation, difficult mask ventilation, and the transition to CICO and scalpel-bougie-tube rescue. 6 min read 0 comments ](https://mdster.com/blog/septic-shock-rsi-and-cico-a-difficult-airway-case-discussion) [ ![Borderline Personality Disorder Crisis: Safe ED Medication Choices](https://mdster.com/storage/blog/images/borderline-personality-disorder-crisis-safe-ed-medication-choices.jpg) Case Discussion ### Borderline Personality Disorder Crisis: Safe ED Medication Choices A case discussion for psychiatry trainees on managing acute borderline personality disorder crisis in the ED, with practical guidance on benzodiazepines, promethazine, overdose safety, and DBT. 7 min read 0 comments ](https://mdster.com/blog/borderline-personality-disorder-crisis-safe-ed-medication-choices) [ ![Fellowship of the College of Physicians and Surgeons Pakistan (FCPS Part II) Study Tips for Obstetrics & Gynaecology](https://mdster.com/storage/blog/images/fellowship-of-the-college-of-physicians-and-surgeons-pakistan-fcps-part-ii-study-tips-for.jpg) Study Tips ### Fellowship of the College of Physicians and Surgeons Pakistan (FCPS Part II) Study Tips for Obstetrics & Gynaecology Practical FCPS Part II study tips for OB-GYN trainees: build a theory-clinical plan, prioritize high-yield cases, practice TOACS, and avoid the mistakes that cost marks. 6 min read 0 comments ](https://mdster.com/blog/fellowship-of-the-college-of-physicians-and-surgeons-pakistan-fcps-part-ii-study-tips-for) [ MDster home ](/ "MDster home") Master your medical exams with evidence-based learning. 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