Physiological Context and Clinical Problem
The normal progression of the first stage of labor relies on synchronized processes. On one hand, myometrial contractile activity increases; on the other hand, anatomical dilatation of the cervix occurs.
In clinical practice, however, clinicians frequently encounter pathological conditions where cervical dilatation lags. Such tissue rigidity or dystocia hinders normal fetal descent and requires mandatory pharmacological intervention to accelerate labor progress.
Pharmacological Classification
To address delayed cervical dilatation, the pharmacological arsenal is divided into two main groups:
- Drugs of choice (most frequently used) — prostaglandins (dinoprost, dinoprostone).
- Alternative agents (less commonly prescribed) — muscarinic antagonists (e.g., atropine).
Differentiation from Other Myometrial Agents
In clinical pharmacology, it is important to clearly distinguish between agents that stimulate the birth canal and those with opposing effects:
- Stimulation of rhythmic uterine contractions: oxytocin, pituitrin, and dinoprost are used to enhance labor. It is crucial not to confuse them with tocolytics (atosiban, salbutamol), whose role is to suppress uterine contractions.
- Management of postpartum hemorrhage (atony): in the early postpartum period, oxytocin and ergometrine (ergot alkaloids) are used to induce strong tonic vascular contractions. In this setting, tocolytics are strictly contraindicated, as uterine relaxation would only exacerbate bleeding.
Limitations of Ergometrine Use
Ergot derivatives, specifically ergometrine, possess a powerful tonic effect on the myometrium but have strict safety boundaries.
This agent is categorically not used for labor induction or augmentation during pregnancy or labor. The reason is the high risk of severe fetal hypoxia. This condition arises from an excessive increase in myometrial basal tone and disruption of normal uteroplacental blood flow.