Stages of labor

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Stages of labor


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Stages of labor

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brachial plexus injury in p. 457

Budd-Chiari syndrome and p. 401

contraction prevention p. 654

endometritis after p. 665

Graves disease and p. 348

low birth weight p. 658

misoprostol induction p. 408

neonatal flora p. 175

oxytocin p. 652

oxytocin for induction of p. 364

postpartum mood disturbances p. 585

preterm, as common cause of death p. 277

progesterone levels after p. 654

Sheehan syndrome after p. 351

stress incontinence and p. 624

C-section deliveries


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Labor, also called parturition, describes the hard work of delivering a baby!

It specifically refers to the process which starts with uterine contractions which cause cervical changes which allow the fetus to be delivered vaginally, and ends with delivery of the placenta.

Labor typically begins at some point when the fetus is considered full term—between 37 and 42 weeks’ gestation.

In the third trimester, before labor starts, a woman might have a plug of mucus and blood fall out of the opening to the cervix, sometimes called a “bloody show”.

Other times the amniotic sac might rupture, sometimes called “water breaking”.

Either of these can trigger the onset of labor and so-called true labor contractions.

These guys have to be distinguished from the milder and ineffective false labor contractions, also called Braxton Hicks contractions (or sometimes called practice contractions).

Once they start, true labor contractions progress in frequency, duration, and intensity, and they can feel like waves that build up to a peak intensity and then gradually decrease.

The contractions pull on the thick tissues of the cervix, causing it to efface or get thinner and also dilate or open up, so then the fetus can leave the uterus and enter the world.

From the moment true contractions begin to the baby’s delivery usually takes about 12 to 18 hours for a first-time pregnancy, and about half that time for subsequent pregnancies.

Although, as any mother knows, this time can vary a lot!

Even though labor is a continuous process, it can be broken down into three stages.

Additionally, this first stage is subdivided into two phases.

The first phase is the early phase or latent phase, and usually lasts up to 20 hours, or until the cervix dilates to 6 centimeters.

At first, there are irregular contractions that occur every 5 - 30 minutes and last about 30 seconds each, causing the cervix to dilate from 0 cm to about 3 cm and efface from about 0% - 30%.


Labor is the process by which the fetus and placenta leave a woman’s uterus, thereby ending the pregnancy. It occurs roughly 40 weeks after the beginning of the last menstrual period. Vaginal delivery involves three stages of labor: the shortening and opening of the cervix, descent and birth of the baby, and the delivery of the placenta. 


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  2. "Physiology" Elsevier (2017)
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  4. "Principles of Anatomy and Physiology" Wiley (2014)
  5. "Reassessing the labor curve in nulliparous women" American Journal of Obstetrics and Gynecology (2002)
  6. "Second-stage labor duration in nulliparous women: relationship to maternal and perinatal outcomes" American Journal of Obstetrics and Gynecology (2009)
  7. "A comparison of active management and expectant management of the third stage of labour: a Swedish randomised controlled trial" BJOG (2011)

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