Conditions and contraindications for instrumental delivery
The application of obstetric forceps requires perfect preparation of the birth canal and an accurate assessment of the fetal condition. Any deviation from the rules threatens severe complications.
Mandatory conditions for the procedure:
- Exclusively a live fetus.
- Full dilation of the uterine cervix (otherwise, the cervix may be caught, extending the tear into the lower uterine segment).
- Absence of the amniotic sac (tension of the membranes can cause premature placental abruption).
- The fetal head must be in the narrow part of the pelvic cavity (sagittal suture in the direct or nearly direct position).
- The urinary bladder must be emptied (catheterization is a mandatory preparation step).
Absolute contraindications: The application of forceps is prohibited in cases of fetal death (a destructive operation is indicated in this case), incomplete cervical dilation, prematurity, and malformations (hydrocephalus, anencephaly). The instrument must not be used if the head is high (applied to the pelvic inlet or in the wide part) or if there is a threat of uterine rupture.
Operation technique: Triple rule and 4 steps
The procedure is performed in the standard obstetric position (legs flexed and abducted) under intravenous or regional anesthesia. Safe delivery is based on the triple rule:
- Order: The left blade is inserted with the left hand into the left half of the pelvis (controlled by the right hand). The right blade is inserted with the right hand into the right half (controlled by the left hand).
- Position: The tips of the blades point toward the pelvic axis of the birth canal. The grasping of the head is strictly biparietal (across the ears), along the large oblique diameter.
- Traction: The force vector coincides with the pelvic axis line (downward toward the legs, forward toward the abdomen, backward toward the back).
Four classic steps of the operation:
- Insertion and placement of the blades. The doctor inserts fingers into the vagina, protecting the soft tissues. The left branch is held like a pen, with the lower edge resting on the 3rd finger of the internal hand. The blade slides between the 2nd and 3rd fingers without deviating from the head and without pressing on the vaginal fornices. Then the right branch is inserted similarly.
- Locking and trial traction. The branches are locked using the Bush hooks. To avoid compressing the head, a folded cloth is placed between the handles. Trial traction is mandatory: the doctor pulls with the right hand while checking with the index finger of the left hand on the head to see if it moves synchronously with the instrument.
- Traction (extraction). The doctor sits with elbows pressed against the body (to protect against excessive force). The right hand specifically grasps the handles (2nd and 4th fingers on the hooks, 3rd between the branches), and the left hand is placed on top. Traction is synchronized with pushing efforts or their rhythm is simulated under anesthesia.
- Removal of the forceps. After crowning of the head, the lock is opened. The right blade is removed first, followed by the left. Subsequent delivery of the torso proceeds naturally.
Features in various presentations
Occiput anterior position: Traction is performed until the suboccipital fossa reaches under the pubic symphysis. Then the doctor stands to the side, delivers the head with the right hand, and protects the perineum with the left hand (an episiotomy is performed if there is a risk of rupture).
Occiput posterior position: Traction is directed downward until the large fontanelle is under the symphysis. Then the vector is changed anteriorly to flex the head and deliver the occiput. Important: before the onset of head extension and the delivery of the brow and face, an episiotomy is mandatory.
Atypical forceps (head in the wide part of the pelvis): Today they are used extremely rarely due to the colossal risk of trauma. The blades are applied biparietally, but in the oblique diameter of the pelvis opposite to the position of the sagittal suture. One blade is inserted stationarily, and the second ("wandering") blade is moved within the pelvis.
Complications and alternative methods
Instrumental delivery carries risks. If the forceps slip (due to incorrect grasping or size mismatch) or if the extraction attempt is unsuccessful, the procedure is immediately terminated.
Tactic in case of failure:
- For a live fetus—emergency Cesarean section.
- In case of fetal death—destructive operation.
Even with ideal technique, injuries to the mother (tears of a narrow or inflamed vagina) and the fetus (facial nerve palsy, cephalhematoma) are possible. The birth of a child in asphyxia is often related not to the forceps themselves, but to preceding intrauterine hypoxia.
Vacuum extraction of the fetus: An alternative method of extracting a live fetus. It is based on creating negative air pressure (vacuum), causing the cup of the device to suction onto the head, allowing traction (extrahere — to pull out).
Briefly: answers to topical questions
What types of destructive operations are used in obstetrics?
The following types of destructive operations (embryotomies) are used in obstetrics:
- Craniotomy — dissection of the skull of the presenting and subsequent head in order to reduce its size.
- Cleidotomy — transection of the clavicles.
- Decapitation — separation of the fetal head from the torso.
- Evisceration — removal of internal organs.
- Spondylotomy — dissection of the spine.
Currently, these interventions are used extremely rarely, as they are highly traumatic for the mother. The least traumatic of these is craniotomy.
What fetal injuries can occur when using obstetric forceps?
Various mechanical damage to the child's tissues and organs can occur when using obstetric forceps. The main fetal injuries include:
- Facial nerve palsy — damage to the peripheral nervous system.
- Cephalhematoma — soft tissue injury, the risk of which increases significantly when the instrument is applied to the head in the wide part of the pelvic cavity.
Damage to the central nervous system and fetal bones is also possible. The risk of injury increases in the presence of chronic or acute hypoxia.
What special instruments are used to perform a craniotomy?
The following special instruments are used to perform a craniotomy:
- Bullet forceps or Muzeux forceps — used to grasp and fix the skin of the fetal scalp.
- Phenomenov perforator — a spear-shaped instrument with a cross-shaped handle for creating an opening in the skull.
- Blot perforator — a scissor-like instrument for perforation.
- Large curette — inserted into the perforation hole to destroy and remove brain tissue (excerebration).
- Cranioclast — an instrument for extracting the fetus (this step is no longer used).
What are the indications for fetal vacuum extraction?
The indications for fetal vacuum extraction are the following obstetric situations:
- Uterine inertia — when drug therapy is ineffective.
- Onset of acute fetal hypoxia — requires rapid extraction.
- Low transverse arrest of the sagittal suture.
- Maternal conditions — states requiring immediate delivery at the end of the second stage of labor.
- Difficulty in delivering the fetal head — during Cesarean section.
A mandatory prerequisite for the procedure in uterine inertia or hypoxia is the location of the fetal head in the narrow cavity of the lesser pelvis.
Rule of hands and sides: Left blade — with the Left hand — into the Left half of the pelvis. Right blade — with the Right hand — into the Right half.
Class and exam questions
In which cases are destructive fetal operations resorted to?
They are performed in case of intrauterine fetal demise, especially if attempts to apply obstetric forceps have failed and the fetus cannot be extracted otherwise.
How to ensure that the forceps will not slip during tractions?
For this purpose, a trial traction is performed. The physician pulls the handles with one hand while using a finger of the other hand to check the contact of the instrument with the head. If the head does not follow the forceps, the instrument is applied incorrectly.
Why must the physician sit down during head extraction?
A sitting position with feet firmly pressed to the floor and elbows pressed against the torso prevents the development of excessive physical force. This protects the mother and fetus from severe trauma during rapid extraction.
Can forceps be applied when the cervix is not fully dilated?
Categorically no. This is an absolute contraindication, as the instrument will grasp the edges of the cervix, leading to its rupture with possible extension to the lower uterine segment.
What else to study on this topic
- Biomechanism of labor in anterior and posterior occipital presentations
- Surgical technique and suturing of episiotomy
- Prevention and management of cephalhematoma and facial nerve palsy in the newborn
- Regional anesthesia in labor: indications and technique
- Anatomy of the female pelvis: planes, dimensions, and the axis of the pelvis
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