Authors’ reply


  • Tracey Johnston MD FRCOG,

  • Tara Selman PhD MRCOG

Dear Sir

We thank Dr Poddar for his interest in our article, and for his comments. As stated, the purpose of the article was not to rehearse the basic techniques of vacuum extraction but to inform the readership of some tips to improve the success rate and reduce morbidity when vacuum is used. We agree that ultrasound used by appropriately trained individuals can assist with determining the position of the vertex in labour, but would strongly caution that knowing where the occiput is does not necessarily help with determining the position of the flexion point. A vacuum cup should not be placed unless the flexion point can be identified. If a clinician is unable to determine the position on vaginal examination and requires the assistance of ultrasound, we would question the ability to accurately determine where the flexion point is in most cases, and would therefore suggest that a cup should not be applied. If the reason for not being able to determine the position is excessive caput, as explained in the article this may suggest a degree of disproportion, and can also prevent a good seal with the cup being achieved, and in these cases careful selection of the correct instrument to achieve delivery is paramount.

With respect to choice of vacuum equipment, we would again like to point out that not all devices are the same, and choosing the appropriate instrument for individual clinical cases is essential. There must therefore be a choice if outcomes are to be maximised. Caution must be exercised when relying on the Kiwi Omnicup versus alone. In randomised controlled trials, the Kiwi device has a higher failure rate compared to conventional (metal or silastic cup) ventouse (30.1% versus 19.2%[1]; 34% versus 21%[2]), especially with malposition (48%[1] and 56%[2]), a higher association with sequential use of instruments (22% versus 10%[1]), a higher number of detachments[1] (44% versus 18% of at least one detachment) but no difference in trauma rates. Although individual operators have demonstrated excellent outcomes with the Kiwi device, the results of these randomised controlled trials must be acknowledged.

On a final note, the markings on the tubing of the Kiwi device in relation to the introitus depend upon the station of the vertex and how deflexed the head is. The cup must always be placed over the flexion point which does not necessarily equate with placing the cup ‘as deeply as possible posteriorly’. The key to success is appropriate patient selection, use of the correct instrument, and ensuring cup placement over the flexion point.