From the Guidelines
A 3 cm cervix is not definitively indicative of latent labour, as it can be at the transition point between latent and active phases of labor. According to the most recent study published in the American Journal of Obstetrics and Gynecology in 2023 1, the active phase of labor begins at various degrees of dilatation when the rate of dilatation transitions from the relatively flat slope of the latent phase to a more rapid slope. Key factors to consider in determining the phase of labor include:
- Cervical dilatation pattern, which is the most reliable indicator of the onset of the active phase and the normality of its progression
- The rate of dilatation, which increases from the negligible or absent slope of the latent phase to the more rapid progression of the active phase
- Serial vaginal examinations, which should be undertaken at least every 2 hours to determine when the rate of dilatation increases
The study emphasizes that assessing uterine contractions, for example, by palpation or using Montevideo Units, is of limited value in determining if a patient is in the active phase 1. Instead, the dilatation pattern is alone as being reliable for prospectively identifying the onset of the active phase and the normality of its progression, provided it is being graphed serially in labor.
In clinical practice, a 3 cm cervical dilation may warrant closer monitoring to determine the true labor phase and appropriate management, as the distinction between latent and active labor matters for management approaches 1. Healthcare providers should assess not only cervical dilation but also effacement, fetal station, and contraction patterns to determine the true labor phase.
From the Research
Definition of Latent Labour
- Latent labour is the initial phase of labour, characterized by the cervix undergoing rapid remodeling, softening, and becoming thinner and more compliant 2.
- During this phase, the cervix may dilate modestly, but the duration of latent labour can vary significantly, with a normal limit of approximately 20 hours in nulliparous women and 14 hours in multiparous women 2.
Cervical Dilation and Latent Labour
- A cervical dilation of 3 cm is not necessarily indicative of latent labour, as the definition of latent labour has been redefined to extend until about 6 cm of cervical dilation, regardless of parity or whether labour was spontaneous or induced 3.
- The American College of Obstetricians and Gynecologists (ACOG) defines active labour as starting when the cervix is dilated 6 cm 4.
Assessment of Latent Labour
- Continuous monitoring of cervical dilation and fetal head station during labour can provide accurate assessment of labour progression and enable timely recognition of abnormal labour patterns 5.
- Nursing support during the latent phase of labour is crucial, and nurses should have a low threshold to use safe and effective interventions to manage abnormal progression in the first stage of labour 3, 6.