Operative vaginal deliveries are classified based on the status of the foetal head and the degree of rotation needed. These classifications include outlet delivery, low delivery, and mid delivery, each defined by specific foetal head positions and rotations during the extraction process.¹

The use of VAD is contraindicated in certain foetal conditions, such as bleeding disorders and demineralising diseases. Additionally, the procedure is discouraged before 34 weeks of gestational age. Obstetricians must ensure that all prerequisites are met and the patient consents to the care plan before proceeding.¹

The use of VAD is considered ‘appropriate’ in certain circumstances such as maternal exhaustion, non-reassuring foetal heart rate, prolonged second stage of labour, or specific maternal conditions.¹

Prerequisites include a fully dilated cervix, previously ruptured membranes, engagement of the foetal head, known head position, foetal weight estimation, adequate pelvic dimensions, adequate anaesthesia (often an epidural), the maternal bladder has been emptied, and the patient's agreement after informed consent.¹

A backup plan (typically a caesarean section) should be in case of failure, recommends Tonismae et al.¹

Vacuum delivery systems often preferred over forceps

According to the authors, VAD systems, are often preferred over forceps. These systems come in various designs, with soft-cup devices minimising neonatal scalp injuries. One of the most popular is the Kiwi Complete Vacuum Delivery System.^1,2

Tonismae et al stress that adequate training is crucial when using a VAD system to minimise complications. An operator and at least one assistant should be present, with additional personnel available for infant resuscitation if required.¹

The technique involves careful application of the vacuum cup to the foetal scalp, ensuring proper placement for flexion, descent, and rotation of the vertex during traction (see below).¹

The procedure requires skilled monitoring and coordination, and suction is applied during contractions. Multiple detachments are discouraged, with caesarean section considered if detachment occurs more than two to three times.¹

Maternal and newborn complications that indicate vacuum-assisted delivery is needed

Maternal complications may include vaginal lacerations and pain, while newborn complications may range from scalp lacerations to intracranial haemorrhage. Although complications are generally rare, practitioners should be vigilant and prepared for potential adverse outcomes.¹

Continuous re-evaluation during the delivery process is essential, with a focus on avoiding rocking motions and excessive torque. The maximum time for vacuum delivery  and the acceptable number of detachments remain uncertain, but recommendations suggest limiting vacuum application time to 20-30 minutes and restricting detachments to two to three.¹

Tonismae et al emphasise optimal cup placement over the foetal head flexion point, intermittent suction application, and careful consideration of vacuum application time and number of pulls. Traction should follow the pelvic curve to maintain foetal head flexion, with adjustments as the head descends.¹

The crucial initial step in the VAD process involves identifying the correct attachment point on the baby's scalp, located 3cm anterior to the posterior fontanelle along the midline of the sagittal suture.³

The VAD device is then applied to create a secure attachment using vacuum pressure, resulting in the formation of a fluid-filled elevated region on the scalp known as the caput succedaneum chignon. This localised oedema, induced by the vacuum, serves as a mechanical interface between the scalp and the device.³

The formation of the chignon enables the clinician to use the VAD handle during contractions to assist the mother by promoting descent through the birth canal. This process is especially beneficial when the foetal head is malpositioned, as the correctly positioned VAD induces flexion and descent, facilitating spontaneous rotation to the ideal occiput anterior position.³

The clinician should carefully monitor the baby's position and employ counter-traction if needed to maintain device position during traction. Traction is a two-handed exercise, with one hand preventing cup tilting and the other monitoring descent without the bony skull moving, indicating an obstruction. This technique aids in gauging and regulating tractive force, crucial during outlet deliveries.³

The entire procedure typically lasts around 10 minutes with two to three pulls, exerting forces up to 115N. The success rate exceeds 80% when using a commonly available VAD device like the Kiwi, according to Goordyal et al.³

The device remains in use until the baby's head crowns, representing the most significant resistance. The vacuum is released after the foetal chin emerges from the introitus.³

In some cases, VAD may be required for rotational delivery, involving a redirection of traction according to the station of delivery and along the axis of the maternal pelvis.³

Patient counselling is essential

Effective communication with patients is crucial, allowing time for counselling on the purpose, procedure, hazards, and alternatives. The discussion should also address potential outcomes if the vacuum procedure fails, considering cesarean delivery as an option.¹

Conflicting data on the impact of failed vacuum assistance on cesarean outcomes necessitate careful consideration and transparent communication with expecting parents.¹

Benefits of the Kiwi system compared to conventional vacuum delivery

Siggelkow et al compared the safety and efficacy of the Kiwi OmniCup system with conventional vacuum delivery by examining completed births, drop-off rates, and various secondary outcome measures for both instruments.⁵

The retrospective study included 4682 births, with 217 undergoing operative vaginal deliveries (4.6%). Of these, 79 used conventional vacuum extraction (37%) and 138 utilized the Kiwi system (63%).⁵

The Kiwi OmniCup, a single-use instrument with an integrated hand pump, features a flexible suction and traction element designed for ease of insertion centrally.⁵

Lateral traction leads the traction element into a groove, facilitating rotation of the head, especially in anterior and posterior cephalic presentations.⁵

Results indicated that the use of the Kiwi system led to a significant reduction in episiotomies compared to the control group (61% vs 76%).

Despite the higher incidence of cup detachment with the Kiwi system, the study found similar rates of maternal and foetal injuries for both systems.⁵

Bodner-Adler et al aimed to assess the correlation between mediolateral episiotomy and severe perineal trauma during Kiwi vacuum deliveries in nulliparous women.⁶

Analysing 572 cases from 2010 to 2015, the study found a 96% success rate in completing births with a 4% failure rate. Among the subjects, 65% underwent Kiwi vacuum delivery with episiotomy.⁶

The occurrence of third- or fourth-degree perineal tears was 6.6%, and it was significantly lower in women with Kiwi vacuum deliveries combined with episiotomy.⁶

Additionally, the rates of perineal tears of all degrees, vaginal tears, and labial trauma were significantly reduced when Kiwi vacuum delivery was accompanied by mediolateral episiotomy.⁶

This suggests that performing a mediolateral episiotomy is associated with a decreased risk of severe perineal tears and other genital tract trauma in Kiwi vacuum deliveries.⁶

Conclusion

Operative vaginal delivery, particularly with VAD systems like the Kiwi system, plays a crucial role in obstetric care. Personalised approaches to operative vaginal delivery should be based on clinical judgment and patient-specific factors.

The Kiwi system, with its soft cup design and unique features, proves advantageous over conventional vacuum delivery, significantly reducing episiotomies. Additional studies highlight the benefits of Kiwi vacuum deliveries with mediolateral episiotomy, showing significantly lower rates of severe perineal tears and genital tract trauma.

Effective patient communication and proper training are essential for successful VAD procedures, establishing it as a viable alternative to cesarean section with fewer complications in well-trained hands.

References

1. Tonismae T, Canela CD, Gossman W. Vacuum Extraction. [Updated 2023 Jul 29]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459234/
2. Laborie. Kiwi® Complete Vacuum Delivery System. Updated 2022. [Internet]. Available from: http://bit.ly/3RQqlkc
3. Goordyal D, Anderson J, Alazmani A, Culmer P. An engineering perspective of vacuum assisted delivery devices in obstetrics: A review. Proc Inst Mech Eng H, 2021.
4. Kiwi Complete Vacuum Delivery System with PalmPump^TM. Updated 2022. [Internet]. Available at: https://p1.aprimocdn.net/laborie/asset_id_100080_Original%20file.pdf
5. Siggelkow W, Schwarz N, Beckmann MW, et al. Comparison of Obstetric Efficacy and Safety of the Kiwi OmniCup with Conventional Vacuum Extraction. Geburtshilfe Frauenheilkd, 2014.
6. Bodner-Adler B, Kimberger O, Käfer A, et al. Management of the Perineum during Delivery with the Kiwi Omnicup: Effects of Mediolateral Episiotomy on Anal Sphincter Tears in Nulliparous Women. Gynecol Obstet Invest, 2018.