What is pregnancy labor?
The onset of labor is the most anticipated event of pregnancy. Many pregnant women fear they will miss the early signs of labor and be unprepared for the delivery of their child. Fortunately, the body provides several clues that the onset of labor is approaching. There also are signs of pre-labor that indicate that the body is preparing for delivery in the weeks to come. Since a normal gestation is 40 weeks, signs of pre-labor may be apparent at 38 or 39 weeks' gestation. In most cases, labor begins between 37 and 42 weeks after the onset of the last menstrual period. Of course, in some cases, labor may begin prematurely. Although gestational age can be helpful in predicting when the signs of labor or pre-labor will develop, there is no proven way to predict precisely when labor will begin.
What causes pregnancy labor?
No one knows exactly what triggers the onset of labor. Some researchers think that hormonal changes within the fetus cause the placenta to produce increased levels of a substance known as corticotrophin-releasing hormone. This changes the balance of the mother's hormones, which have kept the uterus in a relaxed state. Once the process is triggered, the cervix begins to soften and thin out. In most cases, contractions signal the initiation of labor.
True pregnancy labor vs. false pregnancy labor
How do I prepare for pregnancy labor and delivery?
It is important for both you and the health-care professional (for example, family doctor, obstetrician, midwife, or nurse practitioner) to plan an appropriate course of action once labor begins. Important topics to discuss include the choice of a hospital or birthing center, the anticipated travel time to the facility, and what personal items will be necessary during the stay. Such considerations should be considered long before the anticipated onset of labor.
What are pregnancy labor signs and symptoms?
- Also referred to as the baby "dropping", the term "lightening" refers to the descent of the baby downward into the pelvis.
- Often, women experience less shortness of breath, as the diaphragm extends downward and the lungs have more room to expand.
- A feeling of heaviness or pressure may be felt in the pelvis, and the frequency of urination may increase.
- With the first term pregnancy, lightening usually occurs several weeks prior to the onset of labor.
- As the cervix thins and begins to dilate in preparation for delivery, small capillaries burst and cause a pink or brown vaginal discharge. The cervix begins to soften in anticipation of labor ("ripening").
- Cervical mucus, produced by glands lining the cervix, is expressed as the descending fetal head exerts pressure on the cervix. Blood-tinged mucus (i.e. the "mucus plug" or "bloody show") may be discharged from the vagina due to pressure from the fetal head on the cervical glands.
- Bloody show can occur anywhere from hours to several weeks prior to the onset of labor.
- If bleeding from the vagina is profuse, there may be a problem with the placenta, and the provider of obstetrical care should be notified immediately.
- Some women notice a burst of energy a few days prior to going into labor.
Nausea and diarrhea
Braxton Hicks contractions
- Several weeks prior to the onset of actual labor, the woman may develop irregular contractions of mild intensity. They tend to increase in strength and frequency as the onset true labor approaches.
- Braxton-Hicks contractions are also called "false labor pains," as they do not cause any change in cervical dilatation or effacement (i.e. thinning).
Rupture of the membranes ("water breaks")
- Rupture of the membranes refers to disruption of the amniotic sac that surrounds the baby, usually resulting in leakage of the amniotic fluid from the vagina. This fluid may be expelled as a sudden gush or as a slow trickle. Although most women will be contracting when the membranes rupture, in some cases it may occur prior to the onset of labor. In these latter cases, labor usually ensues shortly after the membranes rupture. If spontaneous leakage of fluid from the vagina occurs, the designated obstetrical care provider should be notified immediately.
When to call a health-care professional for pregnancy labor and delivery
- If you suspect rupture of your membranes
- If you have vaginal bleeding (more than bloody show), fever, or severe abdominal pain
- Any time that you have signs of labor or pre-labor before 37 weeks' gestation
- If you have severe headaches, changes in vision, or abnormal swelling.
- If you notice a sudden decrease in fetal activity.
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Medically reviewed by Wayne Blocker, MDl Board Certified Obstetrics and Gynecology
REFERENCE: Funai, E.F., MD., et al. "Management of normal labor and delivery." UpToDate. Updated: Aug 24, 2016.