Vacuum extraction: core concept and instruments
The vacuum extraction method consists of artificially enhancing the mother's expulsion forces. Unlike the application of obstetric forceps, this procedure does not replace the pushing efforts, but only assists them. This is precisely why it requires the obligatory active participation of the parturient woman.
Historically, obstetrics utilized the Malmstrom apparatus with metal cups (ranging from 7.6 to 15.2 cm in diameter) and an electric pump. Due to the high risk of trauma to the fetal head tissues, it is used extremely rarely today. The modern standard is the disposable Kiwi system with a manual vacuum pump. It employs two types of cups:
- Plastic (rigid): equipped with an internal foam layer. Considered universal and provides the most effective fixation.
- Silicone (soft): features a protective cap that is removed immediately before insertion. It is less traumatic, but does not fixate firmly enough on the head.
Indications and absolute contraindications
The procedure is performed for uterine inertia (if medical therapy is ineffective), developing acute fetal distress, low transverse arrest of the sagittal suture, and also for obstructed delivery of the head during a Cesarean section (CS). Sometimes the method is used for maternal diseases requiring immediate termination of the second stage of labor.
Strict conditions are necessary for a safe intervention:
- Live fetus.
- Full dilation of the uterine os and absence of the amniotic sac.
- Location of the head in the narrow cavity of the pelvis (or at the transition from the wide to the narrow cavity), when the sagittal suture approaches the anteroposterior diameter.
Contraindications include a dead or severely premature fetus, hydrocephalus, anencephaly, and face presentation. A vacuum extractor must not be applied if there is incomplete cervical dilation or a high station of the head (appressed to the pelvic inlet or located in the wide cavity). Furthermore, the method is absolutely prohibited in severe maternal pathologies (preeclampsia, eclampsia, hypertension, decompensated heart defects) when pushing efforts must be completely avoided.
Surgical technique and traction rules
Specific preparation is not required, but the urinary bladder must be emptied using an elastic catheter. Intravenous and inhalation anesthesia are strictly contraindicated—the woman must push effectively.
Before insertion, the surgeon checks the airtightness of the cup on their palm. The labia majora are spread with the left hand, and the cup is inserted with the right hand (rigid one by its lateral surface, soft one in a folded state) and placed on the head. The procedure is performed under strict manual control with the fingers of the vaginal hand to avoid pinching the maternal soft tissues (vaginal walls, edges of the cervix). In the occiput anterior presentation, the center of the Kiwi cup is placed 3 cm posterior to the posterior angle of the posterior fontanelle.
A manual pump is used to create the initial negative pressure (100 mmHg), followed by the working pressure (400–600 mmHg), guided by the green color of the indicator. Tractions are performed strictly synchronously with pushing efforts after a short pause. The direction of traction changes as the head advances:
- Occiput anterior presentation: first pulled downward until the suboccipital region fits under the pubic symphysis, then forward until the head is completely born.
- Occiput posterior presentation: tractions downward until the posterior fontanelle is fixed under the pubic symphysis (1st point of fixation, flexion occurs), then backward to deliver the head after the suboccipital pit approaches the coccyx.
- Sinciput presentation (posterior view): pulled toward oneself until the forehead is fixed under the pubic symphysis (1st point of fixation), then forward to deliver the occipital tuberosity (2nd point of fixation), after which the head extends.
If the cup slips off, the attempt may be repeated. If unsuccessful after two attempts, it is necessary to switch to the application of obstetric forceps. An episiotomy is performed according to indications.
Breech extraction
This manual maneuver is used for the most rapid termination of the 2nd stage of labor in breech presentation. The procedure is indicated when the opportunity to perform a Cesarean section has been missed or as a final stage after a classic combined internal podalic version.
Depending on the situation, different grasping techniques are used:
- In footling or complete breech presentation, the fetus is extracted by one or both feet.
- In frank (pure breech) presentation, the grasp is performed by the inguinal fold.
Historically, the method was used for placental abruption (premature separation of a normally implanted placenta), eclampsia, and acute fetal hypoxia. In modern practice, this procedure is resorted to primarily for extracting the second twin or for the delivery of a dead fetus.
Conditions for performance are similar to vacuum extraction: full cervical dilation, absence of the amniotic sac, and strict compliance of the maternal pelvic dimensions with the parameters of the fetal aftercoming head. However, unlike vacuum extraction, full anesthesia is required here—general intravenous or continuous regional anesthesia.
Briefly: answers to topical questions
What complications for the mother and fetus may arise after the use of vacuum extraction?
During the application of vacuum extraction, injuries to the fetal skin and pinching of the maternal soft tissues may occur.
Possible complications:
- Fetal injuries — slipping of the cup (especially a metal one) from the head can lead to skin damage. The metal cups themselves possess a high degree of traumatization.
- Maternal injuries — pinching of soft tissues (vaginal walls, edges of the cervix) between the cup and the fetal presenting part is possible with insufficient manual control.
What stages does the classic manual maneuver for breech extraction consist of?
The classic manual maneuver in fetal breech presentation consists of sequentially releasing the arms and delivering the head.
The operation includes the following stages:
- Release of the first arm — the arm facing posteriorly (toward the perineum) is always delivered first.
- Release of the second arm — the fetal torso is rotated by 180° to bring the anterior arm to the perineum and subsequently extract it.
- Extraction of the aftercoming head — delivery of the head in accordance with the direction of the pelvic axis (for example, using the Mauriceau–Smellie–Veit maneuver).
What anatomical parts do classical obstetric forceps consist of?
Classical obstetric forceps consist of two halves, or blades. Each blade includes three parts: the spoon, the lock, and the handle.
Characteristics of the instrument elements:
- Lock — a simple movable mechanism for connecting the left and right blades.
- Handles — straight; their outer surface is ribbed and undulating, which prevents the obstetrician's hands from slipping.
- Busch hooks — located on the outer surface of the handles near the lock and serve as a support for the obstetrician's fingers during fetal extraction.
The vector rule in occiput anterior presentation: first pull "Under the pubic bone" (downward), then — "Straight to the abdomen" (forward).
Class and exam questions
What is the fundamental difference between vacuum extraction and the application of obstetric forceps?
When using a vacuum extractor, active participation of the parturient woman is mandatory (she must push), since the device only enhances her own efforts. Forceps, on the other hand, can be used even when pushing efforts are completely absent.
What type of anesthesia is used in vacuum extraction?
Inhalation and intravenous anesthesia are strictly contraindicated. For successful fetal extraction, the woman must be conscious and push effectively.
What to do if the vacuum extractor cup slips off the fetal head?
Re-application is permitted, but no more than two times in total. If the head does not yield to traction after two attempts, it is necessary to switch to the application of obstetric forceps.
What else to study on this topic
- Biomechanism of labor in various types of head engagement
- Technique of performing episiotomy and its indications
- Fetal complications when using metal cups
- Classic combined internal podalic version
- Management of labor and delivery of the second twin in multiple pregnancy
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