Cervical Dilation of 1 cm in Labor
A cervical dilation of 1 cm indicates early latent phase labor, not active labor, and represents the very beginning of the labor process where the cervix is just starting to dilate. 1
Understanding Labor Phases at 1 cm
At 1 cm of cervical dilation, the patient is definitively in the latent phase of labor, which is characterized by slow, gradual cervical change. 2
Key Distinctions Between Latent and Active Phase
- Active phase begins at 5-6 cm according to WHO/FIGO guidelines, with 5 cm as the lower threshold for most women. 1, 3
- ACOG defines active phase onset at 6 cm of cervical dilation, though this threshold has methodological limitations. 1, 4
- At 1 cm, dilatation rates of 0.5-0.6 cm/hour are normal for latent phase labor, particularly in multiparous women. 2
Expected Progression from 1 cm
The median time to progress from 1 cm takes longer than 1 hour per centimeter until reaching 5-6 cm, after which labor accelerates markedly. 5, 6
- In nulliparous women, expect slower than 1 cm/hour progression until approximately 5-6 cm is reached. 5
- After 6 cm, cervical dilation rates typically exceed 1 cm/hour and progress becomes hyperbolic (rapidly accelerating). 6
- The traditional 1 cm/hour threshold throughout labor is unrealistic for most healthy women in early labor. 5
Clinical Management at 1 cm
Hospital Admission Considerations
Do not admit patients to labor and delivery at 1 cm dilation unless there are maternal or fetal complications. 3
- For nulliparous women, consider admission at 4 cm if labor progression rate is ≥1.2 cm/hour, which suggests entry into active phase. 3
- Red flags requiring earlier admission include maternal or fetal compromise, regardless of cervical dilation. 3
Critical Pitfall to Avoid
Do not diagnose protracted or arrested labor at 1 cm dilation. 2
- Labor abnormalities (protraction or arrest) cannot be diagnosed before 6 cm according to current ACOG guidelines, as patients below this threshold are presumed to be in latent phase. 2
- However, this guideline has significant methodological concerns, as some women may enter active phase before 6 cm. 1
Monitoring Expectations
Serial cervical examinations plotted over time are the only reliable method to determine if a patient is progressing normally through latent phase. 1
- Contraction patterns have limited value for determining labor phase, as contractions increase inconsistently in intensity and frequency during early labor. 1
- Individual variation is substantial - some women will progress slowly but normally, while others may show signs of labor dysfunction. 5, 6
Factors Affecting Progression from 1 cm
Multiparity, occipitoanterior fetal position, and absence of epidural analgesia are associated with faster cervical dilation rates. 6