The physiologic process of passing a fetus from the uterus through the vagina to the outside world. Labor is a diagnosis of regular, painful contractions that both dilate (open) and efface (thin) the cervix. Contractions that do not cause cervical dilation and effacement are not technically labor, no matter how painful or regular they are. Likewise, cervical dilation that occurs without contractions is also not labor, but may be cervical incompetence or cervical insufficiency.
Labor is divided into three stages. The first, during which the cervix dilates and effaces to a complete 10cm. The second, when the fetus passes through the vagina, and is delivered. And the third, in which the placenta is delivered.
The First Stage
- Generally the longest, lasting anywhere from a few hours to a full day. Women who have had children before tend to have quicker labors. Length of labor is highly individualized, and the length of the first stage in particular is difficult to predict.
- Begins when regular contractions start, but will often not be diagnosed as labor for several hours when cervical change has occurred.
- Ends when the cervix is completely effaced (thinned out) to 100% and fully dilated (open) to 10cm.
The Second Stage
- Can last anywhere from a few minutes to several hours.
- Usually involves pushing with contractions by the mother.
- Begins when the cervix is 10cm dilated and 100% effaced.
- Ends with the delivery of the fetus.
The Third Stage
- Usually occurs within 15-30 minutes of the fetus being delivered.
- Contractions continue during this stage to help expel the placenta and control bleeding.
- Arrest of descent – During the second stage, if the fetal head stops descending through the mother’s pelvis, she may require an assisted delivery (forceps or vacuum) or c-section.
- Arrest of dilation – If the cervix stops dilating, you may require medications to cause more effective contractions.
- Fetal distress – While this does not usually apply to women going through a pregnancy loss, fetal distress is a potential complication of labor. Fetal distress occurs when the baby does not "tolerate" labor, which is seen through abnormal heart tracings on the fetal monitor. Fetal distress requires interventions by a medical professional, beginning with simple position changes, or IV fluids, and potentially progressing to emergency c-section if a baby is in fatal danger.
- Fetal positioning – In the US, most physicians will not deliver a baby in breech position. If your baby is not positioned with the head down, you will most likely need a c-section. Position of the baby can also affect the length of the second stage. If the baby is occiput posterior ("face up"), delivery may be more difficult.
- Postpartum hemorrhage – After the placenta is expelled, some vaginal bleeding is normal. However, if excessive bleeding continues, a woman may need medication, manual compression by a doctor, or surgery in extreme cases.
- Shoulder dystocia – Occurs after the head delivers, when the shoulder becomes wedged behind the mother’s pubic bone, requiring intervention by a doctor or midwife to complete the delivery.
Pain controlBecause labor contractions tend to cause significant pain, women often seek pain control for labor. Laboring women have several pain control options:
Special considerations for pregnancy loss
Labor may not progress in the expected ways when a woman is experiencing a pregnancy loss. For example, miscarriage occurs before the cervix is completely dilated.
- In early losses, the placenta often delivers with the fetus.
- The cervix is not usually assessed during a miscarriage. It would be assessed in other pregnancy losses. Such as: in pre-term labor, while laboring with a stillborn baby, or during a therapeutic termination when medications are placed against the cervix.
- The first and second stage of labor may be allowed to continue beyond the usual time parameters.
- Your pain control options may be wider in a pregnancy loss because there are no fetal effects to consider.
American College of Obstetricians and Gynecologists, "FAQ: Pain Relief During Labor and Delivery." Accessed 7 December 2011.
Varney, H., Kriebs, J., et al. Varney's Midwifery, Fourth Edition. 2003.
Cunningham, F., Gant, N., et al. Williams Obstetrics, 21st Edition. 2001.