The flexion point is situated on the sagittal suture 3 cm in front of the posterior fontanelle.
The flexion point may be located during vaginal examination by identifying the posterior fontanelle and then moving the finger anteriorly a distance of approximate 3 cm along the sagittal suture. The tip of the finger will mark the flexion point.
If the cup is placed exactly on the flexion point, it assists the delivery of the smallest diameters of the fetal head.
Medisil-Vacuum Extraction Cup
Techniques for using Silicone Cup:
Silicone cups are particularly useful when the exhausted mother has endured the tedium of a long labor, and requires assistance during the second stage. When the fetal head is on the perineum, well flexed and occipito-anterior, the silicone cup device may expedite delivery (FIG 1). The device is unsuitable for mid cavity deliveries with abnormal positions, particularly in the presence of caput and moulding.
For the silicone cup delivery of a baby well below spines with its head flexed in the occipito-anterior position, lithotomy position is not mandatory, given that down-ward traction required for mid cavity deliveries may not be needed. Delivery may be undertaken in the dorsal, left lateral or even squatting positions.
Application of Silicone Cup:
During insertion, the cup is squeezed at its widest point to facilitate gentle introduction through the vulva. The cup must sit easily and comfortably between the fetal head and perineum, and then moved to ensure its correct position over the posterior fontanelle with 30 mm between the cup margin and the bregma. The index finger is passed around the rim to ensure no maternal tissue is pinched between the fetal scalp and the cup, and a vacuum of -20 Kpa is induced. The cup tends to flatten against the fetal scalp. Position and application are rechecked. A full vacuum of –80 Kpa is obtained, and traction commenced at the next uterine contraction (Fig 2). Since a chignon does not form in soft cups, there is no 2-minute waiting period mandatory as in metal cups.
Traction is synchronous with uterine contractions, the right hand supplying firm, gentle tension, and the finger of the left hand on the scalp/rim margin to ensure the head itself descends, and not merely the scalp. Three gentle pulls should be sufficient to deliver most babies especially if the cup is applied correctly and the traction is in the direction of maternal pelvic axis.
An audible hiss suggests traction is too severe and should be momentarily relaxed to prevent cup separation. If this occurs the cup may be reapplied not more than twice, otherwise the procedure must be abandoned. Generally routine episiotomies are superfluous and only cut if obstetrically indicated, for example fetal distress. After delivery of the head, the cup is released and the rest of the infant delivered in the normal way. Traction is not normally applied between contractions, but it may sometimes be helpful to hold the head in place between contractions so it does not move back up the birth canal.