OPERATIVE
VAGINAL DELIVERY
Operative vaginal delivery is a method of
assisting or expediting vaginal vertex delivery through the application of
obstetric forceps or vacuum devices. Assisted or expedited vaginal delivery may
become necessary because of maternal fatigue, prolonged second stage of labor,
or certain types of pulmonary, cardiac, or neurologic disease. When there is
evidence of a nonreassuring fetal status or acute fetal distress, operative
vaginal delivery may provide a safer or more expeditious way of protecting
fetal health.
To perform either forceps- or vacuum-assisted delivery, the cervix must be completely dilated, the fetal presentation must be vertex, and position must be known (and relatively normal). The fetus must be fully engaged, the fetal membranes ruptured, and the patient able to cooperate with the delivery. Operative vaginal delivery is generally contraindicated when the gestational age is less than 34 weeks, there is fetal demineralization, or a clotting disorder is present. In addition, vacuum-assisted delivery is generally not done when there has been prior scalp sampling or multiple attempts at fetal scalp electrode placement.
For successful operative
delivery, adequate maternal anesthesia or analgesia should be ensured in all
but the most extreme circumstances. Whenever possible, the maternal bladder
should be emptied (by catheter). The position of the fetal head must be
ascertained by palpation of the sagittal suture and fontanelles. This can be
supplemented by palpation of the fetal ear in some cases.
Current obstetric
practice has rendered the challenging and difficult forceps deliveries of past
eras exceedingly rare. Midforceps, applied when the vertex has not descended to
the perineum and/or used for rotation of the fetal head when it is not in the direct
occiput anterior (OA) position, are now used only in circumstances where there
is an imminent threat to the well-being or survival of the fetus and a cesarean
section cannot be done expeditiously. Outlet forceps or vacuum extraction,
applied when the vertex is within 45 degrees of the OA and is on the perineum,
is still utilized by experienced operators. There is no clear advantage of one
modality over the other and the choice generally comes down to the particular
preference and experience of the individual responsible for the delivery.
With either modality, it
is critical that the device be carefully placed to avoid iatrogenic trauma to
either mother or baby. It is also important that once placed, the device only
be used to augment maternal expulsive efforts, avoiding both excessive force
and extraneous movements that could result in maternal or fetal trauma: Owing
to the fulcrum effect provided by forceps, uterine or vaginal wall lacerations can result,
and rotational forces applied to the vacuum device can result in laceration or
avulsion of the fetal scalp.
With either device, traction must be coordinated with maternal expulsive efforts. Traction begins in a horizontal or slightly downward (axis of the maternal pelvic canal) manner. To mimic the normal birth process, traction in the horizontal plane continues until the descending fetal head distends the vulva. An episiotomy, if required, may be performed at this point. As the fetal head further distends the vulva, the axis of traction is gradually rotated upward, mimicking the normal extension process of the head as it rotates under the symphysis. Once the brow is palpable through the perineum, the device may be removed and the fetal head delivered by pressure on the perineum (modified Ritgen maneuver). The remainder of the delivery proceeds as with a spontaneous delivery.
