Labor and Delivery
"Labor" and "delivery" describe the process of childbirth. Contractions of the uterus and changes in the cervix (the opening of the uterus) prepare a woman's body to give birth. Then the baby is born, and the placenta follows.
NICHD studies many aspects of labor and delivery: their basic biology, childbirth practices, and management of related problems.
A separate topic covers preterm labor and birth.
About Labor and Delivery
Labor and delivery are the process by which a baby is born, from the body's preparations to when the baby and the placenta leave the womb.
The earliest stage of labor prepares the body for delivery. This is a period of hours or days when the uterus regularly contracts and the cervix gradually thins out (called "effacing") and opens (called "dilation") to allow the baby to pass through.
Once the cervix has opened completely, the woman can begin pushing to deliver the baby. When the baby and placenta come out through the vagina, it is known as a vaginal delivery.1
When does labor usually start?
For most women, labor begins sometime between week 37 and week 42 of pregnancy. Labor that occurs before 37 weeks of pregnancy is considered premature, or preterm.1
Just as pregnancy is different for every woman, the start of labor, the signs of labor, and the length of time it takes to go through labor vary from woman to woman and even from pregnancy to pregnancy.
What is induction of labor?
Induction of labor refers to the use of medications or other methods to induce, or cause, labor. This practice is used to make contractions start so that delivery can occur.1
What are the options for pain relief during labor and delivery?
The amount of pain felt during labor and delivery is different for every woman. The level of pain depends on many factors, including the size and position of the baby, the woman's level of comfort with the process, and the strength of her contractions.
There are two general ways to relieve pain during labor and delivery: using medications and using "natural" methods (no medications). Some women choose one way or another, while other women rely on a combination of the two.
A woman should discuss the many aspects of labor with her health care provider well before labor begins to ensure that she understands all of the options, risks, and benefits of pain relief during labor and delivery before making a decision. It might also be helpful to put all the decisions in writing to clarify things for all those who might be involved with delivering the baby.
What are the stages of labor?
What is natural childbirth?
Natural childbirth can refer to many different ways of giving birth without using pain medication, either in the home or at the hospital or birthing center.
Natural Forms of Pain Relief
- Emotional support
- Relaxation techniques
- A soothing atmosphere
- Moving and changing positions frequently
- Using a birthing ball
- Using soothing phrases and mental images
- Placing a heating pad or ice pack on the back or stomach
- Taking a bath or shower
- Using soothing scents (aromatherapy)
- Acupuncture or acupressure
- Applying small doses of electrical stimulation to nerve fibers to activate the body’s own pain-relieving substances (called transcutaneous electrical nerve stimulation, or TENS)
- Injecting sterile water into the lower back, which can relieve the intense discomfort and pain in the lower back known as back labor
A woman should discuss the many aspects of labor with her health care provider well before labor begins to ensure that she understands all of the options, risks, and benefits of pain relief during labor and delivery. It might also be helpful to put all the decisions in writing to clarify the options chosen.
What is a C-section?
A cesarean delivery, also called a C-section or cesarean birth, is the surgical delivery of a baby through a surgical cut or incision in a woman's abdomen and uterus. After the baby is removed from the womb, the uterus and abdomen are closed with stitches that later dissolve.1
According to the U.S. Centers for Disease Control and Prevention, in 2015, 32% of births were by cesarean delivery—the lowest rate since 2007. Between 1996 and 2008, the number of cesarean deliveries increased by 72%.2
What is vaginal birth after cesarean (VBAC)?
VBAC refers to vaginal delivery of a baby after a previous pregnancy was delivered by cesarean delivery.
In the past, pregnant women who had one cesarean delivery would automatically have another. But research shows that, for many women who had prior cesarean deliveries, attempting to give birth vaginally—called a trial of labor after cesarean delivery (TOLAC)1—and VBAC might be safe options in certain situations.
In fact, NICHD research shows that among appropriate candidates, about 75% of VBAC attempts are successful.2 A 2010 NIH Consensus Development Conference on VBAC evaluated available data and determined that VBAC was a reasonable option for many women.3
NICHD-supported researchers also developed a way to calculate a woman's chances of a successful VBAC.4 Access the calculator. Please note that this calculator only determines the likelihood of successful VBAC; it does not guarantee success.
Women should discuss VBAC and TOLAC with their health care providers early in pregnancy to learn whether these options are appropriate for them. Providers are encouraged to discuss plans for VBAC or refer women to a facility that can support VBAC when it is medically safe to consider.5
When is VBAC appropriate?
VBAC may be safe and appropriate for some women, including those:6
- Whose prior cesarean incision was across the uterus toward its base (called a low-transverse incision)—the most common type of incision. Note that the incision on the uterus is different than the incision on the skin.
- With two previous low-transverse cesarean incisions
- Who are carrying twins
- With an unknown type of uterine incision
- No abdominal surgery
- A lower risk of hemorrhage and infection compared with a C-section
- Faster recovery
- Potential to avoid the risks of many cesarean deliveries, such as hysterectomy, bowel and bladder injury, blood transfusion, infection, and abnormal placenta conditions
- Greater likelihood of being able to have more children in the future
If labor fails to progress or if there is another problem, a woman may need a C-section after trying TOLAC. Most risks associated with C-section after TOLAC are similar to those associated with choosing a repeat cesarean. They include:1,7
- Uterine rupture
- Maternal hemorrhage and infection
- Blood clots
- Need for a hysterectomy
What are some common complications during labor and delivery?
Each pregnancy and delivery is different, and problems may arise.
If complications occur, providers may assist by monitoring the situation closely and intervening, as necessary.
- Labor that does not progress. Sometimes contractions weaken, the cervix does not dilate enough or in a timely manner, or the infant's descent in the birth canal does not proceed smoothly. If labor is not progressing, a health care provider may give the woman medications to increase contractions and speed up labor, or the woman may need a cesarean delivery.3
- Perineal tears. A woman's vagina and the surrounding tissues are likely to tear during the delivery process. Sometimes these tears heal on their own. If a tear is more serious or the woman has had an episiotomy (a surgical cut between the vagina and anus), her provider will help repair the tear using stitches.4,5
- Problems with the umbilical cord. The umbilical cord may get caught on an arm or leg as the infant travels through the birth canal. Typically, a provider intervenes if the cord becomes wrapped around the infant's neck, is compressed, or comes out before the infant.5
- Abnormal heart rate of the baby. Many times, an abnormal heart rate during labor does not mean that there is a problem. A health care provider will likely ask the woman to switch positions to help the infant get more blood flow. In certain instances, such as when test results show a larger problem, delivery might have to happen right away. In this situation, the woman is more likely to need an emergency cesarean delivery, or the health care provider may need to do an episiotomy to widen the vaginal opening for delivery.6
- Water breaking early. Labor usually starts on its own within 24 hours of the woman's water breaking. If not, and if the pregnancy is at or near term, the provider will likely induce labor. If a pregnant woman's water breaks before 34 weeks of pregnancy, the woman will be monitored in the hospital. Infection can become a major concern if the woman's water breaks early and labor does not begin on its own.7,8
- Perinatal asphyxia. This condition occurs when the fetus does not get enough oxygen in the uterus or the infant does not get enough oxygen during labor or delivery or just after birth.3,4
- Shoulder dystocia. In this situation, the infant's head has come out of the vagina, but one of the shoulders becomes stuck.5
- Excessive bleeding. If delivery results in tears to the uterus, or if the uterus does not contract to deliver the placenta, heavy bleeding can result. Worldwide, such bleeding is a leading cause of maternal death.9 NICHD has supported studies to investigate the use of misoprostol to reduce bleeding, especially in resource-poor settings.
Delivery may also require a provider's special attention when the pregnancy lasts more than 42 weeks, when the woman had a C-section in a previous pregnancy, or when she is older than a certain age.
NICHD Labor and Delivery Research Goals
Healthy, safe labor and delivery are fundamental to maximizing health for women and infants in both the short term and the long term.
NICHD research on labor and delivery addresses the following topics, among others:
- Basic biology of labor and how labor progresses
- How to determine the appropriate time for a cesarean delivery when labor does not progress
- New, evidence-based definitions of labor protraction and arrest
- Basic and clinical studies to improve birth outcomes
- Long-term health outcomes of elective cesarean deliveries and labor inductions
- Prevention and management of preterm labor
- Childbirth practices to prevent mother-to-child transmission of HIV and other infectious diseases
- Efficacy and safety of vaginal birth after cesarean delivery
- Effects of different types of childbirth on maternal health
Labor and Delivery Research Activities and Advances
Through its intramural and extramural organizational units, NICHD supports and conducts a variety of research on labor and delivery.