Vacuum extraction (ventouse delivery)

Introduction

Ventouse is an instrumental device designed to assist in delivery by creating a vacuum between the device and the fetal scalp.

The vacuum extractor, introduced by Malinstrom in 1954, is designed to aid in delivery by applying traction to a suction cup attached to the fetal scalp. It allows for the extraction and delivery of the fetal head in situations where the use of obstetric forceps would be difficult or likely to be traumatic. The original metal cups have undergone modifications, and safer silastic cups have been developed. As a result, the vacuum extractor has replaced conventional obstetric forceps, particularly when the fetal head is at a higher station, not well-rotated, or incompletely flexed.

Design of the instrument for vacuum extraction

The Malinstrom vacuum extractor consists of the following components:

1. Specially designed metal cups, with a smaller rim diameter compared to the area above the rim, designed to create a chignon (a raised bump) that can be firmly gripped within the cup. These cups are available in three sizes: 40mm, 50mm, and 60mm.
2. Hollow tubing.
3. A glass trap bottle with a manometer.
4. A chain attached to the cup, which passes through the tubing and attaches to a crossbar and handle used for traction.

Patient selection and pre-requisites criteria

The patient should meet the following criteria for vacuum extraction:

1. The presenting part should be cephalic and preferably well flexed.
2. There should be no evidence of cephalo-pelvic disproportion.
3. The fetal head should be well engaged at a high station, up to +2.
4. There must be a medical indication to hasten delivery.
5. The cervix should be fully dilated, and the membranes should be ruptured.
6. The obstetrician performing the procedure should be well-trained in the use of the instrument.
7. The patient’s urinary bladder should be empty.
8. .Informed written consent must be obtained from the patient.

Indications for Vacuum Extraction

A. Maternal Indications:

• Maternal distress due to exhaustion following a long and painful labor, often caused by disordered contractions.
• Prolonged second stage of labor.
• Maternal medical disorders, such as heart disease, hypertensive disorders, and moderate to severe anemia.
• Elderly primigravidae (older first-time mothers).

B. Fetal Indications

• Fetal distress.
• Cord prolapse (in selected cases).
• Non-rotated head in occipito-transverse position.
• Occipito-posterior position.
• Relatively higher station at +2 or just above.

Contraindications for Vacuum Extraction

• Premature babies.
• Major degree of cephalopelvic disproportion (CPD).
• Soft tissue obstruction in the pelvis.
• Breech and face presentation.
• High station of the head, i.e., above station zero.
• Macrosomia (large baby).
• Intrauterine fetal death.
• Lack of expertise in the procedure.
• Inability to achieve correct application.

Procedure for Vacuum Delivery

1. Place the mother in the lithotomy position and provide emotional support and encouragement.
2. Cleanse the vulval area with an antiseptic solution and drape it with sterile sheets. Prepare other necessary items as for a normal delivery.
3. Ensure that the bladder is empty; catheterize if necessary.
4. Perform a thorough examination to determine the station of the fetal head, position of the occiput, location of suture lines, posterior fontanelle, and assess pelvis and cervical dilatation.
5. Put on personal protective barriers.
6. Check all connections and test the vacuum on a gloved hand.
7. Select the largest cup that can be comfortably introduced and apply it over the fetal scalp, positioning the center of the cup over the flexion point, which is 1 cm posterior to the posterior fontanelle.
8. Assess the position of the fetal head by feeling the sagittal suture line and fontanelle, and identify the posterior fontanelle.
9. Perform an episiotomy if necessary to ensure proper placement of the cup. If an episiotomy is not required, delay it until the head stretches the perineum or the perineum obstructs the axis of traction.
10. Ensure that maternal soft tissues, including the cervical rim or vaginal wall, are not included in the cup.
11. Create suction with a force of 0.2 kg/cm² and gradually increase it at a rate of 0.2 kg/cm² every 2 minutes to achieve a negative pressure of 0.8 kg/cm². Verify the proper application of the cup.
12. Once adequate suction force is achieved, apply intermittent traction during uterine contractions, supplemented by maternal bearing-down efforts. Traction should be maintained during contractions, with the direction of pull corresponding to the birth canal’s axis. Pulling at right angles to the cup ensures proper alignment and prevents cup slippage. Traction should be relaxed between contractions, and the suction force should be temporarily reduced.
13. During traction, place a finger on the scalp next to the cup to assess potential slippage and the descent of the fetal vertex.
14. Between contractions, monitor fetal heart sounds (FHS) and verify the proper application of the cup
15. Typically, delivery is completed within 3-5 pulls over a period of 15 minutes.
16. Once the head is delivered, release the suction, and the cup will slip off, allowing you to complete the delivery as usual.
17. Ensure that the total time of application until delivery does not exceed 20 minutes, as the risk of fetal scalp trauma and intracranial damage increases beyond this point.
18. Administer 10 units of intramuscular oxytocin for the active management of the third stage of labour.
19. Examine the birth canal for tears following delivery and repair if necessary.
20. If an episiotomy was performed, repair it as needed.
21. Indications of vacuum failure include:

• The head does not advance with each pull.
• The fetus remains undelivered after 3 pulls or after 30 minutes.
• The cup slips off the head twice despite proper direction of pull and achieving a maximum negative pressure.

22. In case of vacuum failure, perform a cesarean section.

Complications of vacuum delivery

A. Maternal complications:

• Soft tissue injuries like cervical tear, annular detachment of cervix, vaginal tears, perineal laceration and tears, extension of episiotomy, vaginal wall and perineal haematoma.
• Traumatic post-partum haemorrhage.
• Infection
• Incompetent cervix
• Genital prolapse.

 B.  Fetal complications.

• Hypoxia
• Injury to scalp: Abrasions, laceration and cephalo-haematoma, intracranial injuries, intraventricular and cerebral haemorrhage, particularly when the babies are preterm.
• Neonatal jaundice
• Convulsions
• Shoulder dystocia particularly if baby is large
• Prolonged traction in preterm babies may lead to neurological sequelae.

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