The female hormone oxytocin is produced by the posterior pituitary gland and stimulates uterine contractions. This oxytocic effect is greatest at term. However, oxytocin infusion, which acts similarly to the naturally occurring hormone, may be used in antenatal situations where labor must either be induced to start or must be assisted by increasing the force of uterine contractions. Augmentation of labor is initiated in the active phase of the first stage of labor or in the second stage when labor is failing to progress adequately, placing the fetus and mother at risk. Several conditions can dictate the need for labor to be induced at term or earlier depending on the ability of the fetus to survive extrauterine life. These include gestational age greater than 42 weeks, maternal history of precipitate labor in a multiparous patient, polyhydramnios or hydramnios, Rh isoimmunization, severe preeclampsia near or at term, prolonged premature rupture of membranes, diabetes, abruptio placentae, incomplete or inevitable abortion, and fetal death. The goal of treatment is to stimulate labor as similar to natural labor as possible while ensuring maternal and fetal well‑being and preventing complications associated with oxytocin induction.
Pathophysiology
Oxytocin indirectly stimulates contraction of the uterine smooth muscle by increasing sodium permeability of uterine myofibrils. The threshold for response is lowered when estrogen levels are high. Uterine response increases with the length of pregnancy and active labor. The response mimics labor contractions.
Complications
■ Hyperstimulation syndrome
■ Uterine rupture (particularly with previous uterine scar)
■ Fetal distress
Assessment
Health perception and management
■ Fear
Elimination
■ Urinary frequency
■ Constipation
Cognition and perception
■ Anxiety
Roles and relationships
■ Unhealthy family dynamics
Coping and stress management
■ Stress level
Physical examination
Mental status and behavior
■ Anxiety
■ Fear
Cardiovascular
■ Increased cardiac demand
■ Increased blood pressure
Reproductive
■ Possible hypotonic uterine contractions
Diagnostic Tests
■ Contraction stress test assesses fetal well-being.
■ Pelvic or uterine ultrasonography assesses gestational age and size and the position of the fetus.
■ Lecithin-to-sphingomyelin ratio assesses fetal lung maturity, except in cases of maternal diabetes, Rh incompatibility, or fetal asphyxia.
■ Bishop score is a five-parameter scoring system that estimates the success of induction. The maximum score is 13. The minimum score for induction without the use of a cervical ripening agent is 6.
Teaching checklist
■ Reason for induction
■ Oxytocin use
■ Induction process
■ Importance of concentrating on fetal movements or kick counts
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