Signs of Normal Labor
The primary signs of normal labor include regular uterine contractions that increase in intensity, frequency, and duration, accompanied by progressive cervical dilation and effacement, which is the most reliable indicator of active labor. 1, 2
First Stage of Labor
The first stage of labor consists of two phases:
Latent Phase
- Characterized by slow cervical dilation with a relatively flat slope on the labor curve 2
- Contractions may be irregular and less intense during this phase 2
- No major labor abnormalities occur during this phase except for prolonged duration 2
Active Phase
- Begins when cervical dilation accelerates, regardless of the specific dilation measurement 1
- Identified by serial vaginal examinations (at least every 2 hours) that show increased rate of dilation 2, 1
- Normal dilation rates are ≥1.2 cm/hour for nulliparas and ≥1.5 cm/hour for multiparas 1, 2
- Contractions typically become more regular, frequent, and intense, though these characteristics alone cannot reliably distinguish active labor 2
- Ends with a brief deceleration phase that is often undetected 2
Uterine Contractions
- Regular uterine contractions are a hallmark sign of normal labor 3
- Contractions inconsistently increase in intensity, frequency, and duration throughout the first stage 2
- No abrupt change in contraction characteristics marks the onset of active phase 2
- Later in labor, increased and more painful contractions often signal the beginning of the deceleration phase and fetal descent 2
- Normal contractions should achieve approximately 200 Montevideo Units when measured internally, though this measurement has limited clinical value in determining active labor 2, 4
Cervical Changes
- Progressive cervical dilation is the most reliable indicator of active labor 2, 1
- Cervical effacement (thinning) occurs alongside dilation 3
- The pattern of dilation, when graphed serially, helps distinguish normal from abnormal labor 2
Second Stage of Labor
- Begins at complete cervical dilation (10 cm) 1
- Normal duration is 2-3 hours according to WHO recommendations 1
- Characterized by descent of the fetal head through the birth canal 1
- Accompanied by maternal bearing-down efforts 2
- Ends with delivery of the fetus 1
Third Stage of Labor
Important Considerations
- The duration of normal labor varies significantly between nulliparous and multiparous women 5
- For nulliparas, mean active first stage is 7.7 hours (up to 17.5 hours can be normal) 5
- For multiparas, mean active first stage is 5.6 hours (up to 13.8 hours can be normal) 5
- Mean second stage duration is 54 minutes for nulliparas and 18 minutes for multiparas 5
- Factors that may prolong normal labor include electronic fetal monitoring, ambulation, maternal age over 30 years, and narcotic analgesia 5
Pitfalls in Identifying Normal Labor
- Relying solely on uterine contraction patterns to diagnose active labor is unreliable 2, 4
- Failing to perform serial vaginal examinations may lead to misdiagnosis of labor phase 2, 1
- Misidentifying the transition to active phase can lead to unnecessary interventions 2
- Normal labor often lasts longer than many clinicians expect, leading to premature diagnosis of labor disorders 5
- Inadequate monitoring of relaxation time between contractions can miss signs of fetal distress 6