Residency · Residency · Obstetrics Gynecology

Operative Vaginal Delivery: Forceps and Vacuum

Overview

Operative vaginal delivery (OVD) refers to the use of forceps or a vacuum extractor to assist delivery of the fetal head. It accounts for approximately 3% of US deliveries, a rate that has been declining over decades. OVD serves as an alternative to cesarean delivery in the second stage of labor and requires specific training, proper patient selection, and strict adherence to safety criteria.

Indications

Maternal

Maternal indications include prolonged second stage of labor (more than 3 hours with an epidural or more than 2 hours without in nulliparous women, and more than 2 hours with or more than 1 hour without in multiparous women), maternal exhaustion, and medical conditions where Valsalva or prolonged pushing is contraindicated, such as certain cardiac diseases, cerebrovascular disease, or myasthenia gravis.

Fetal

Fetal indications include a non-reassuring fetal heart rate pattern in the second stage requiring expedited delivery. Piper forceps are specifically designed for the aftercoming head in breech delivery.

Prerequisites (Must ALL Be Met)

All of the following prerequisites must be met before attempting operative vaginal delivery: vertex presentation, fully dilated cervix (10 cm), ruptured membranes, known fetal position (which must be determined accurately), adequate maternal analgesia, clinically adequate maternal pelvis, operator experience with willingness to abandon if unsuccessful, informed consent, an emptied bladder, and a back-up plan for cesarean delivery that is immediately available.

Classification by Station

Outlet

Outlet delivery is defined by the fetal scalp being visible at the introitus without separating the labia, with the skull having reached the pelvic floor and the sagittal suture within the anteroposterior diameter or within 45 degrees. Rotation is 45 degrees or less. This classification carries the highest success rate and lowest complication rate.

Low

Low operative delivery is defined by the leading point of the skull at station +2 or greater (below the ischial spines). It is subdivided into two categories based on whether rotation is 45 degrees or less or greater than 45 degrees.

Mid

Mid operative delivery involves a station above +2 with the head engaged (biparietal diameter past the pelvic inlet). Rotation may or may not be needed. This classification carries higher complication rates and requires significant expertise.

High

High forceps refers to an unengaged fetal head. This is contraindicated and should never be attempted.

<image>Sagittal cross-section of the maternal pelvis showing fetal station levels from -5 to +5 relative to the ischial spines, with labeled zones for outlet, low, and mid operative vaginal delivery classifications</image>

Forceps

Types and Selection

Outlet/Low Forceps (No Rotation)

Simpson forceps are the most commonly used, featuring separated shanks and a cephalic curve. Elliot forceps have overlapping shanks and are useful for round, unmolded heads typically seen in multiparous patients.

Rotational Forceps

Kielland forceps have minimal pelvic curve with a sliding lock and are designed for rotation of occiput posterior (OP) or occiput transverse (OT) positions. They require advanced training, and their use is declining. Tucker-McLane forceps have solid blades and are useful for rotation.

Special Purpose

Piper forceps are designed specifically for the aftercoming head in breech delivery, featuring longer shanks and a reverse pelvic curve.

Forceps Anatomy

The blade has both a cephalic curve (which fits the fetal head) and a pelvic curve (which follows the birth canal). The shank connects the blade to the handle. The lock is either an English lock (fixed, as in Simpson forceps) or a sliding lock (as in Kielland forceps). The handle provides the grip for the operator.

Application Technique (OA Position)

The forceps are assembled and checked before application. The left blade is inserted first, held in the left hand and placed into the left side of the pelvis. The right blade is inserted second, held in the right hand and placed into the right side of the pelvis. The lock is articulated, and it should come together easily -- if it does not, the position should be reassessed. Correct placement is confirmed by checking that the sagittal suture is equidistant between the blades (symmetric application), the posterior fontanelle is one fingerbreadth above the plane of the shanks, and no more than one fingerbreadth of blade is palpable above the symphysis. Traction is applied during contractions with the maternal pushing effort. The direction of traction follows the Pajot maneuver: outward and downward following the pelvic curve, then upward as the head crowns. The forceps are removed after delivery of the head or as it extends over the perineum.

Forceps Rotation

OP to OA rotation requires 180 degrees. Manual rotation is preferred initially, with forceps rotation if manual rotation fails. Kielland forceps were designed for this purpose but their use is declining. OT positions require 90-degree rotation. All rotation should be gentle, using the wrist rather than the arm.

Vacuum Extraction

Types of Vacuum

Soft cup devices (silicone or silastic) such as the Kiwi and Mystic have a lower scalp injury risk but a higher failure rate. Rigid cup devices (metal Malmstrom or M-cup) have a higher success rate but greater scalp injury risk. Disposable handheld devices like the Kiwi are most commonly used and allow single-operator use.

Technique

The appropriate cup size is selected and placed over the flexion point, located on the sagittal suture approximately 3 cm anterior to the posterior fontanelle. Proper placement maximizes success and minimizes complications. It is essential to check that no maternal tissue (cervix or vaginal wall) is trapped under the cup. Vacuum is gradually built to 500 to 600 mmHg. Traction is applied during contractions with the maternal pushing effort, following the pelvic curve (downward, then outward, then upward). The vacuum is released and the cup removed after delivery of the head.

Pop-Off Rules

If the cup detaches (pops off), fetal position and cup placement should be reassessed. Vacuum is generally abandoned after 2 to 3 pop-offs, with some institutional variation. Total vacuum application time should be less than 20 to 30 minutes. Each pop-off increases the risk of neonatal scalp injury.

<image>Diagram of vacuum cup placement on the fetal head showing correct positioning over the flexion point (3 cm anterior to the posterior fontanelle on the sagittal suture) versus incorrect paramedian placement that leads to deflexion and higher failure rates</image>

Complications

Maternal

Maternal complications include vaginal and cervical lacerations (more common with forceps), perineal tears (third and fourth degree tears occur in 8 to 15% with forceps versus 4 to 8% with vacuum), episiotomy-related extensions, hemorrhage, bladder injury (rare), and anal sphincter injury.

Neonatal

Forceps-specific neonatal complications include facial nerve palsy (a compression injury that is usually transient), facial bruising and lacerations, skull fracture (rare), and intracranial hemorrhage (rare). Vacuum-specific neonatal complications include cephalohematoma (5 to 15%), which is a subperiosteal hemorrhage that does not cross suture lines, and caput succedaneum (chignon), which is normal soft tissue edema under the cup that resolves. The most dangerous vacuum complication is subgaleal hemorrhage, occurring in less than 1% of cases. This involves bleeding between the periosteum and galea aponeurosis, a large potential space that can accommodate enough blood to cause hemorrhagic shock. Signs include boggy, fluctuant scalp swelling crossing suture lines, increasing head circumference, pallor, and tachycardia, requiring emergent neonatal team involvement and resuscitation. Retinal hemorrhage and intracranial hemorrhage can also occur.

Sequential Instrumentation

Use of vacuum followed by forceps (or vice versa) significantly increases the risk of neonatal injury. It is generally discouraged unless an expert operator determines that the benefit outweighs the risk. If one instrument fails, cesarean delivery should be strongly considered.

Choosing Between Forceps and Vacuum

Forceps have a higher success rate (approximately 95%) compared to vacuum (approximately 80 to 85%). Forceps cause more maternal injury, including lacerations and anal sphincter injury, while vacuum causes more neonatal scalp injuries, including the risk of subgaleal hemorrhage. Forceps are capable of rotation using specialized instruments, while vacuum has limited rotational capability. Forceps require a higher level of operator skill, while vacuum requires moderate skill. Training in forceps is declining while vacuum technique is more widely taught.

When to Abandon

An operative vaginal delivery should be abandoned when the forceps do not articulate easily, when there is no descent with appropriate traction over 2 to 3 pulls, when the vacuum detaches 2 to 3 times, when there is concern for fetal or maternal injury, or when the total duration of vacuum application exceeds 20 to 30 minutes. The decision to abandon an operative vaginal delivery reflects good clinical judgment, not failure.

Clinical Pearls

Accurate determination of fetal position is the single most important step before any operative vaginal delivery. An unrecognized occiput posterior position is a common cause of failure and injury.

Outlet forceps and vacuum carry the lowest risk and highest success. Mid-station procedures should only be attempted by experienced operators.

Forceps cause more maternal perineal trauma while vacuum causes more neonatal scalp injuries. The choice should be based on the clinical scenario and operator expertise.

Subgaleal hemorrhage is the most dangerous neonatal complication of vacuum extraction. Neonatal head circumference and vital signs should be monitored closely after delivery.

Sequential use of forceps and vacuum (or vice versa) significantly increases neonatal injury risk and should generally be avoided.

Kielland forceps rotation for occiput posterior position has largely been replaced by manual rotation followed by direct traction, or cesarean delivery.

Declining OVD training is a major concern. Simulation-based education is essential for maintaining competency.

References

• ACOG Practice Bulletin No. 219: Operative Vaginal Birth (2020)
• Ramphul M et al. Instrumental delivery and ultrasound: a multicentre randomized controlled trial (ISRCTN72230496). BJOG. 2014
• Murphy DJ et al. Cohort study of operative delivery in the second stage of labour and standard of obstetric care. BJOG. 2003;110:610-615
• O'Mahony F et al. Choice of instruments for assisted vaginal delivery. Cochrane Database Syst Rev. 2010
• Bahl R et al. Outcome after instrumental delivery in relation to station at instrumental delivery. Obstet Gynecol. 2007;109:505-511

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