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Vacuum delivery injuries - what are they ?

Serious injuries associated with vacuum delivery include subgaleal hematoma and intracranial bleeding.  Less serious and superficial injuries are cephalhematoma, scalp lacerations, and abrasions.  Too often in vacuum delivery, steps are taken to avoid the less serious injuries and cosmetic effects, such as using one of a number of soft cups.  However, the evidence shows that use of soft cups does not reduce the incidence of serious injury or, indeed, cephalhematomas. Furthermore, it should be realized that scalp abrasions will heal without leaving any lasting traces  and cosmetic effects will disappear in a few days.  

Vacca states “The chignon or vacuum-induced caput succedaneum, cup markings, abrasions and cephalhaematomas are less serious scalp effects that may cause anxiety to parents and birth attendants by their cosmetic appearances, but only rarely are they associated with long-term sequelae for the infant

Vacca1 states “The chignon or vacuum-induced caput succedaneum, cup markings, abrasions and cephalhaematomas are less serious scalp effects that may cause anxiety to parents and birth attendants by their cosmetic appearances, but only rarely are they associated with long-term sequelae for the infant.2,3  Parents will be reassured if they receive appropriate explanation and assurances that the lesions will disappear without leaving any permanent marking on the infant’s scalp.”

What causes vacuum delivery injuries?

 Injuries to the scalp from vacuum delivery are likely to be associated with:

   a)   Incorrect cup placement, 

   b)   Excessive traction force,

   c)   Improper traction technique.
 These often result in cup “pop-off,” which increases the chance and severity of injury.  Serious injuries and superficial injuries such as abrasions and lacerations are not caused by the vacuum cup itself, be it hard or soft, but are usually caused by pulling too hard or in the wrong direction on a cup placed over the wrong spot on the baby’s head
  


How can vacuum delivery injuries be avoided?

 Serious and superficial injuries are avoided by placing the cup over the flexion point of the fetal head and exerting light traction in line with the pelvic axis.  With spontaneous delivery the smallest diameters of the fetal head are usually presenting in the birth canal and the fetus autorotates in most cases as it descends.  Vacuum delivery is sometimes needed when arrest of descent occurs because the smallest diameters of the fetal head are not presenting.  The goal of vacuum delivery is to correct the malposition and present the optimal diameters so that descent and autorotation can occur. 

The center of the cup should be placed over the flexion point which is located 3cm forward of the posterior fontanel in the midline over the sagittal suture.

Cup Placement
The center of the cup should be placed over the flexion point which is located 3cm forward of the posterior fontanel in the midline over the sagittal suture.  In malpositions of the fetal head, proper placement cannot be achieved with soft cups in most cases because of their high profile and their handles/suction tubing set at right angles to the body of the cup (See Figure 1).  The only cups that can be properly placed consistently in cases of fetal malposition have a low profile and suction tube in the same plane as the cup  (See Figure 2)
 

Figure 1
In malpositions of the fetal head, proper placement cannot be achieved with soft cups in most cases because of their high profile and their handles/suction tubing set at right angles to the body of the cup

                     Figure 2
The only cups that can be properly placed consistently in cases of fetal malposition have a low profile and suction tube in the same plane as the cup

Gimovsky states “The most critical, single step in a vacuum extraction is cup placement.”4  For tips on locating the flexion point using the Vacca maneuver, cup selection, and cup placement click here for a quick reference.

 Traction Force & Technique
With the cup placed over the flexion point the smallest presenting diameters will line up properly with the birth canal provided axis traction is applied and only light traction should be needed to effect delivery.  The vacuum operator just helps nature get back on track by using the vacuum to line up smallest presenting diameters.  The mom provides the expulsive effort and the baby autorotates by nature as it does in spontaneous delivery when the head presents correctly.  “... oblique traction, and multiple cup detachments are believed to increase the risk of serious fetal injury.”5 

How can vacuum delivery results be evaluated?

 A good way to evaluate the results of a successful vacuum delivery or investigate the cause of a failed vacuum is to check for and document the cup placement location after delivery.  The cup location will be evident from the chignon or cup marking on the baby’s head.


Incorrect Cup Placement                         
Incorrect Cup Placement 

Correct Cup Placement
Correct Cup Placement

 Correctly determining fetal position and properly placing a vacuum cup is not always easy.  However, if delivery results and cup placement are evaluated after each delivery improvements will be realized.  Vacuum injuries can be avoided with proper education and technique. When injuries do occur the cause should be investigated by determining cup placement location for future improvement. 

 

The Kiwi OmniCup with Traction Indicator is used to determine the amount of force exerted in each traction.

Kiwi OmniCup with Traction Indicator

The Kiwi OmniCup with Traction Indicator is used to determine the amount of force exerted in each traction.  A traction force of 20 lbs. was found to be sufficient by Vacca6.  If the cup is placed properly,  delivery will usually occur; furthermore, by limiting traction force to 20 lbs. risk of injury to the fetus will be avoided when the cup is not over the flexion point and delivery is not imminent.

  
Reference:

  1. Vacca A. The trouble with vacuum extraction.  Current Obstet and Gynecol. 1999;9:41-45.
  2. Garcia J, Anderson J, Vacca A, Elbourne D, Grant A.  Chalmers I. Views of women and their medical and midwifery attendants about instrumental delivery using vacuum extraction and forceps. J Psychosom Obstet Gynaecol. 1985; 4: 1-9.
  3. Vacca A. Vacuum extraction: fact and opinion.  In: Cosmi EV. Montanino G (eds.) Prodeedings of the 2nd World Congress on labor and delivery.  London: The Parthenon Publishing Group, 1998; 64-69.
  4. Koscia KL, Gimovsky ML. Vacuum Extraction: optimizing outcomes, reducing legal risk.  OBG Management April 2002, 88-94. 
  5. Schwartz ML, O’Grady JP.  The obstetric vacuum extractor: recent innovations and best practices.  Contemporary Ob/Gyn 2002;5:114-126.
  6. Vacca A. Operative vaginal delivery: clinical appraisal of a new vacuum extraction device.  Aust N Z J Obstet Gynaecol 2001; 41: 2: 156-160.

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