Signs of Impending Labor
Before the onset of active labor, certain symptoms may appear, signaling the approach of labor. These include irregular contractions, a sensation of fetal descent, and a small amount of blood-tinged vaginal discharge (commonly referred to as "bloody show"). These are collectively known as threatened labor (or prodromal labor).
Irregular Contractions
Also known as "false labor," irregular uterine contractions may occur due to increased uterine myometrial sensitivity before the onset of labor. The characteristics of these contractions include:
- Inconsistent frequency, short duration, and prolonged irregular intervals;
- Absence of progressively increasing intensity of contractions;
- Often occurring at night and disappearing by morning;
- A lack of accompanying changes such as cervical shortening or dilation;
- Suppression with the use of sedatives.
Sensation of Fetal Descent (Lightening)
As the presenting part of the fetus descends into the pelvis and becomes engaged, the uterine fundus lowers. Pregnant women may feel a sense of relief in the upper abdomen compared to before. However, the descent of the presenting part may compress the bladder, leading to frequent urination.
Bloody Show (Show)
Within 24 to 48 hours before the onset of labor, slight bleeding may occur as the fetal membranes near the internal cervical os separate from the uterine wall, causing capillary rupture. This blood mixes with cervical mucus to produce a blood-tinged mucus discharge, referred to as the "bloody show." The appearance of the bloody show is considered a relatively reliable sign that labor is imminent. However, if vaginal bleeding is more substantial, resembling or exceeding menstrual flow, pathological causes of antepartum hemorrhage should be considered, with placenta previa and placental abruption being the most common possibilities.
Diagnosis of Labor
The onset of labor is characterized by regular and progressively intense uterine contractions lasting 30 seconds or longer, with intervals of 5–6 minutes. These contractions are accompanied by progressive effacement (shortening) of the cervical canal, cervical dilation, and the descent of the presenting part of the fetus. The process cannot be inhibited by sedatives. The determination of labor requires close observation of the frequency, duration, and intensity of uterine contractions. Following sterilization of the vulva, a vaginal examination is performed to assess the length, position, texture, and dilation of the cervix, as well as the station of the presenting part. The Bishop scoring system is commonly used to evaluate cervical readiness for labor and to estimate the likelihood of a successful trial of labor. The system assigns a total score of up to 13 points; a score greater than 9 indicates nearly certain success, a score of 7–9 indicates a success rate of 80%, a score of 4–6 suggests a 50% chance of success, while a score of 3 or below predicts failure.
Table 1 Bishop scoring system for cervical ripeness
Total Labor Duration and Stages of Labor
The total course of labor refers to the time from the onset of regular uterine contractions to the delivery of the fetus and placenta. Clinically, labor is divided into three stages:
First Stage of Labor (Cervical Dilation Phase)
The first stage, also referred to as the cervical dilation phase, begins with the onset of regular contractions and ends when the cervix is fully dilated to 10 cm. This stage is further divided into a latent phase and an active phase:
- Latent Phase: A period of slow cervical dilation that typically does not exceed 20 hours in primiparous women and 14 hours in multiparous women.
- Active Phase: A period of accelerated cervical dilation, which begins when cervical dilation reaches approximately 4–5 cm. In some cases, it may start as late as 6 cm. The phase ends when the cervix is fully dilated (10 cm). During this phase, the rate of dilation should be at least 0.5 cm per hour. Current practice often uses 5 cm of cervical dilation as the threshold for entering the active phase, with efforts made to minimize unnecessary interventions before this point.
Second Stage of Labor (Fetal Expulsion Phase)
The second stage, also known as the fetal expulsion phase, begins with complete cervical dilation and ends with the delivery of the fetus.
For women without epidural anesthesia, the second stage should not exceed 3 hours for primiparous women and 2 hours for multiparous women.
When epidural anesthesia is used, the duration may be extended by 1 hour, with a maximum of 4 hours for primiparous women and 3 hours for multiparous women.
It is important to emphasize that prolonged delays should not occur before assessing labor progress. For primiparous women whose second stage of labor exceeds 1 hour, close monitoring is recommended. If it surpasses 2 hours, comprehensive evaluation by an experienced clinician is required to assess maternal and fetal conditions and determine further management.
Third Stage of Labor (Placental Expulsion Phase)
The third stage, also known as the placental expulsion phase, extends from the delivery of the fetus to the expulsion of the placenta. This usually takes about 5–15 minutes and should not exceed 30 minutes.