Theories of Labor
The uterine contractions during labor are influenced by four hormones, the primary of which is oxytocin with estrogen, fetal cortisol, and prostaglandin. These four hormones’ actions are counteracted by progesterone, which prevents contraction.
- Progesterone decreases on the ninth month because of the placental degradation after it reaches its lifespan limit. This starts contractions, and the mother enters labor and delivery.
- Oxytocin Theory: the pressure of the fetal head on the cervix in late pregnancy stimulates the posterior pituitary gland to secrete oxytocin, which cases uterine contractions.
- Uterine Stretch Theory: the stretching of the uterus to an adequate size results in increased production of prostaglandin and oxytocin.
- Prostaglandin Theory:
- Aging Placenta Theory: after maturation, more pressure is exerted on the fundal portion, the usual placental site, and the most contractile portion of the uterus. It is believed that the resultant diminished blood supply to the area causes contraction.
- Progesterone Deprivation Theory
Premonitory Signs of Labor
- Lightening: descent/dipping, dropping of the presenting part to the true pelvis.
- Increased Braxton Hicks contractions 3 to 4 weeks before labor
- Increased maternal energy/burst of energy; nesting behavior
- Decrease in weight by 2 to 3 pounds, 1 to 2 days before labor.
- SHOW: blood-tinged mucus discharge from the cervix shortly before or during labor
- Ripening of the Cervix: becomes as soft as butter
- Rupturing of the Bag of Water: an occasional sign, and is an indication for hospitalization.
- Progressive Fetal Descent: increased backache and sacroiliac
Components of Labor
- Power: uterine contractions, pushing of the mother.
- Contractions: from the myometrium of the upper uterine segment fundus.
- Ability of the Mother to Push, done only once effacement and dilatation are complete (10 cm, 100%).
- Passageway: the cervix, vagina, perineum, and pelvis.
- Passenger: number, size, attitude, presentation, position, lie
- Psyche
- Placental Factors
Stages of Labor
- Dilatation and Effacement: lasting from the onset of labor to complete dilatation and effacement. It is divided between three phases:
| Area | Latent | Active | Transitional |
|---|---|---|---|
| Cervical Dilatation | 0-3 cm | 4-7 cm | 8-10cm |
| Duration | <40 seconds | 40 to 60 seconds | 60 to 90 seconds |
| Frequency | more than q5min | q3-5min | q90-120sec |
| Intensity | Mild to Moderate | Moderate to Strong | Strong |
| Client’s Mood | Cooperative | Less Cooperative | Uncooperative |
- Expulsion: lasting from complete dilatation and effacement until the expulsion of the baby.
- Placenta: lasting from the expulsion of the baby to the expulsion of the placenta.
- Recovery: lasting from expulsion of the placenta to the first two hours postpartum.