The physiological process of having a baby can be described in stages, and understanding these stages can be incredibly helpful for easing anxiety, making plans for any medical care you might receive, and making choices around how, where, and with whom you’d like to give birth. We outline the stages of labor and some considerations pregnant or expecting parents might find beneficial as they prepare for childbirth.
What is labor, really?
We see it in movies (sorta), we hear stories, and some of us may have had the honor of witnessing someone’s labor, but most of us don’t really see or experience labor until we are in the midst of our own parenting journeys. Read on for some foundational info on the primary mechanism of labor and what makes it tick.
Labor is commonly described in three stages. We will describe the general sequence of a typical physiological labor, understanding that many people’s experiences will be shaped by medical interventions, as well as the preparation and support with which they enter the experience. While the mechanisms of labor are quite universal, they don’t necessarily feel, look, or strengthen in exactly the same way between individuals, who come to the experience with their own health history, pregnancy experience, personal preferences, and even perceptions of sensation.
What is a contraction?
One of the first things to understand about labor is the primary mechanism by which a baby is aided down and out of the pregnant parent’s pelvis. The uterus is a pear-shaped organ with dynamic muscle fibers running vertically, horizontally and even diagonally in multiple layers. It is a versatile organ that is held in place in the bony pelvis by flexible ligaments, and expands significantly in size to accommodate a growing fetus throughout pregnancy, along with the placenta and amniotic sac.
The top of the uterus is called the fundus, and the tissue making up the lowest portion of the uterus is called the cervix - this tissue is shaped somewhat like a donut, with a very small opening in the center that will expand over the course of labor to allow the baby to pass out of the uterus, through the birth canal - or vagina - and out into the world. During pregnancy, the cervical opening is very small or closed, and the cervix itself is quite thick, about 2-3cm. The cervix is also usually “sealed” with protective mucus, and it protects the environment of sensitive fetal development from outside bacteria or materials that could pose any risk.
When the smooth muscle fibers of the uterus tighten in a wave-like motion, squeezing from the top down, this is called a contraction. People who menstruate may feel cramps at the onset of their period - these are shallower, less forceful contractions that help the uterus to shed the tissue we commonly refer to as “period blood”. Contractions can also sometimes be felt as a pulsing or wave-like sensation during orgasm.
Hormones in Labor
Oxytocin is the hormone that is released from the brain, enters the bloodstream, and signals the uterus to contract. It is also related to feelings of bonding, connection and social well-being when it is released and circulated as a neurotransmitter in the brain. As a contraction encourages a baby’s movements towards the vaginal canal and their head presses down against the cervix, more oxytocin is released, which encourages continued contractions and creates a feedback loop of the momentum of labor. Natural oxytocin also can decrease the release of the stress-hormone, cortisol, while cortisol can inhibit the effects of oxytocin.
Synthetic oxytocin, usually in the form of “Pitocin”, stimulates contractions effectively. However, it does not cross into the brain when given intravenously, so Pitocin does not directly create the same psychological effects as endogenous oxytocin. Because Pitocin and other “augmentation” drugs may increase the frequency and strength of labor contractions at higher levels of intensity then would occur naturally, their use in labor must be monitored closely to avoid potential risks to the fetus or birthing person.
The layers of the uterus are moderated by hormonal activity and stimulation of the nervous system. The sympathetic nervous system (also often referred to as the “fight, flight, freeze” response) can be very helpful in relation to the exertion and effort - and any effects of strenuous exercise - that are part of natural labor “stress”. But if the amount of stress-related hormones, like cortisol, get out of balance, the parasympathetic nervous system - the “rest, heal, connect and digest” system to which oxytocin is tied - can be thrown off, and this imbalance can lead to physiological “distress” in the parent or baby and even stall labor.
The Three P’s
We’ve described the mechanism of a contraction and some of the hormonal signals involved in uterine activity during labor. Now we lay out the three main elements that coordinate during labor - how they work together can determine the details of labor, such as duration, sensation and potential challenges to navigate.
Your baby is the most precious parcel in the world, and while the distance from your uterus to your arms is quite short, they have to make a bit of a journey to get from the very protected, perfectly fitted, nourishing environment of the amniotic sac and uterus into the outside world. This is by design, as a developing fetus is safest tucked deep within their parent’s body, where they can receive nutrients and are protected from the elements.
We now understand that in utero, a baby’s lungs are one of the last things to develop. When they do, the fetus releases a hormone that is thought to signal the other hormones and mechanisms of labor to start. But that isn’t all the baby does! However they are positioned at the start of labor, they must make their way out of the uterus, which is contained within the limits of the bony (albeit mobile and slightly flexible) pelvis. To do this, a baby will turn, spiral and descend the pelvis as labor progresses.
The starting position of your baby and their movements over the course of labor can impact their journey. Gentle movements and stretches throughout pregnancy can support a more spacious pelvis, but there will always be some babies who are not positioned exactly head down with their chin tucked and all their limbs close to their body. Such variations, including which way the baby is facing, can impact the progress of labor, which is one reason changing positions and movement during labor can be so helpful.
It is also helpful to remember that the baby’s skull is not fully hardened before birth - its bony plates are actually designed to squeeze a little bit to fit the approximate 10-centimeter diameter of the pelvic outlet. After birth, a newborn’s skull will round out and fuse in place in the familiar shape we know as adults.
The pelvis itself is not an exact structure between all human beings. Birthing people may have a pelvis that is particularly round, or more oblong, and every once in a while - in less than 1% of cases - a person might have a particularly narrow pelvic outlet that is smaller than the space their baby needs to pass. Most of the time, however, a pelvis is “sufficiently” open and mobile enough for a baby to pass through it, especially when a birthing person is supported in shifting positions, working with gravity, moving instinctually, and mitigating stress and fear - which can affect sensation as well as bodily tension.
Generally, the upper portion of the bony pelvis is wider than the lower portion where the baby exits. Earlier in labor, the baby is navigating the upper portion, and rotating to navigate the hard boundaries of the pelvis, before descending into the lower portion of the pelvis and then being born. To do this, most babies turn in a series of motions referred to as the “cardinal movements” of labor. This helps them to align their head, shoulders and body with the most spacious parts of the pelvis as they move down and out during labor.
Individual labors may include different levels of intensity, and birthing people may find that their labor progresses forward, pauses, and at times slows down depending on energy levels, nourishment, environment, or temporary stressors, which can be a normal way your body naturally moderates the energy needed to complete the process safely. All in all, the “powers” of the birthing person include their natural strength, but also the involuntary strength of their uterine muscle, which is supported by nourishment, rest and a moderately active lifestyle during pregnancy.
Because the mechanism of a contraction is itself involuntary, most birthing people have the capacity and strength to birth whether or not they believe it - but some people - especially if they have conditions related to muscular function, cardiac or respiratory function, mobility limitations, postural or structural functional challenges, or conditions of the soft tissues, may need medical assistance. Even in these cases, individualized care, physical and emotional support, and collaborative, informed decision-making is essential for the appropriate and dignified care of each birthing person.
The “powers” of labor also refer to the psyche - does a birthing person feel trust in their body? Are they feeling particularly frightened, or are they cultivating calm in their body despite the new experience? Do they feel supported in making decisions and moving or behaving as they need to through labor? How confident are they about their capacity to birth, and what do they believe about labor and childbirth? While these questions are not direct determinants of someone’s labor outcome, because the psyche is so closely related to our emotions, stress levels, and in turn our hormonal and physiological processes, considering the psychological aspects of labor is a worthy aspect of birth preparation and support.
Stages of Labor
We’ve laid the foundation for the elements that come together in the physiological process of human labor. Hormones, instincts, fetal participation, anatomy and individual energy and health all synchronize in what is a rather impressive combination of muscular, chemical and psychological processes resulting in birth. Here we lay out the physical stages of labor and some considerations for each.
If you are planning for a vaginal delivery, you and your provider may discuss plans around laboring at home and connecting with your provider there, at a birth center, or at a hospital. Understanding the general sequence of the stages of labor can aid that planning, as well as normalize the length and processes of labor, which are rarely represented realistically in film or television.
1st Stage - Effacement and Dilation
The first and usually longest part of labor is effacement (thinning) and dilation (opening) of the cervix. At first, the cervix is a few centimeters thick, and comparable to the firmness of the tip of your nose. As it softens and becomes thinner, it is more like the texture of your relaxed lips. This is called effacement and is measured in percentages - a 100% effaced cervix is practically paper-thin. In this stage, the cervix is also slowly opening - as our cervix dilates, your health care provider may offer to measure the opening in centimeters using their fingers. One centimeter is a little less than half an inch. Over the course of labor, a cervix will dilate to about 10 centimeters, or about 4 inches.
This first stage of labor makes up the majority of the time of labor, and is generally described in three parts:
1. “Prelabor” describes the subtle effacement and thinning that can happen before someone notices regular labor contractions. Many people are already partially effaced and up to 1-2cm dilated when their labor contractions start. Some people feel “warm-up contractions” before a regular contraction pattern occurs - read more about Braxton-Hicks and other variations of early contractions here.
2. “Early labor” refers to the beginning of dilation, up to about 5-6cm. This can take place over hours or sometimes days, and is usually the longest part of labor for a first time birthing person. Most people experience a portion of early labor at home because the contractions are relatively far apart.
- Contractions may occur about 15 minutes apart or less. Check out our tips on timing contractions here. Contractions may be up to about a minute or so at this stage.
- Recommended activities are to rest, continue light activities or movement as desired, and prioritize getting nourishing meals full of protein, vegetables and whole grains in - think of it as resting and adding calories before an athletic event!
- Also helpful can be bonding with your partner, baby or support people, and any activities that help you feel relaxed, comfortable, connected or pleasurable! These types of feelings encourage the central nervous system function and hormonal activity described above.
- If eating, sleeping, changing positions or taking a hot shower make the contractions go away, you may still be in the earliest stages or “prelabor” zone, so be patient with yourself, hydrate, eat, entertain and rest.
3. “Active Labor” is more familiar to popular perceptions of labor, when a laboring person is needing to focus on their contractions more with focused breathing, movement and possibly sounds. “Active” is used to describe this experience because the contraction pattern tends to pick up and the rate of dilation increases after 6cm. A laboring person may be less talkative as labor progress continues, which is a good sign of their brain’s instinctual focus on the task at hand.
- Contractions are more frequent and may be stronger, occurring every five or four minutes, or even more frequently, and last about one minute or more.
- Using comfort measures and positions to cope, rest between contractions and focus may be helpful. Hands-on support, rhythmic movements, changing positions regularly, and using deep breaths - or anything that helps a laboring person to focus, manage sensation and feel safe - can be provided by a partner, doula or other support person.
- Continuing to eat high-energy snacks like honey sticks or nut bars, and hydrating with electrolytes, or broth, supports energy levels through active labor.
- The intensity of active labor contractions also often cues the body to release endorphins, “feel good” chemicals that mediate painful sensation and produce pleasure. Comfort measures can support this process.
- Most providers encourage their clients to contact them when labor becomes more active as things can move more quickly at this time, although it can still be some hours before childbirth, especially for first time parents. Using the 4-1-1 or 5-1-1 rule is a good way to assess whether you might be in active labor.
4. “Transition” is just what it sounds like and is often an intense, but comparatively brief, part of the first stage of labor. This refers to the internal cervical change and the baby’s descent lower in the pelvis that transitions a laboring person to complete 10cm dilation. The pressure, opening and increased hormones of this process can be both physically and psychologically intense, and may come with other symptoms such as shaking, temperature fluctuations, and a shift in emotional response, such as frustration or feeling weepy.
- Contractions are quite close together, as little as two minutes apart, and may last for longer than they did previously. This is normal and also requires a lot of energy on both the laboring person and baby’s part.
- Breaks are shorter and less frequent, so continuous support and encouragement to breathe deeply, hydrate with small sips, and rest in between contractions is key. Some people may need additional touch and verbal support, while others may respond best to a quiet, meditative atmosphere, or even some private time alone (with someone nearby) or with a trusted support person.
2nd Stage - Pushing and Birth
Despite its popularity in film, this stage of labor is much more brief than the first stage. Once someone’s cervix is completely dilated, contractions will continue, along with any additional efforts on the part of the birthing person in the form of pushing.
Sometimes, the body creates a natural pause in contractions upon reaching 10cm cervical dilation, other times, a laboring person will feel the pressure of their baby’s descent as rectal pressure similar to the urgency of a bowel movement. If they do not feel such pressure, they may be supported in resting before pushing, and if they cannot feel such pressure due to the use of an epidural, they may be encouraged to “labor down”, or wait for involuntary contractions to do part of the job before exerting effort in pushing.
Some people prefer to be coached to push, although overcoaching can lead to less oxygenation or pushing out of sync with the natural rhythm of contractions, which can be exhausting. Pushing too early or too frequently can distress a baby, or injure soft tissues that are still gradually stretching open for birth. This is one reason many providers will want to confirm complete dilation before pushing commences. Breaks between pushing contractions allow both parties to receive oxygen, recover, and build energy for the next push.
Many people find their own pushing rhythm, and the length of this phase can vary depending on the position of both baby and birthing person, and if the person has given birth before. Many providers will make suggestions or offer interventions if pushing continues for more than a few hours - however, first time laborers may need time to ‘learn’ to push effectively, and so monitoring parental and fetal vitals as well as trying different positions are both used to support the process safely.
Hormonally, a brief surge of adrenaline helps to renew strength and minimize painful sensation, and many people feel relief at pushing. “Crowning” describes the baby’s head or presenting part at the vaginal opening, when it does not recede between contractions - this lasts only a few moments. Many providers will offer guidance and a warm compress to support the perineal tissue and help a birthing person deliver their baby gently, other times the baby will crown and be born quite quickly. People push in all kinds of positions when given the freedom to do so, although some settings prioritize positions that make it easy for providers to see and assess progress.
3rd Stage - The Placenta
The moment of childbirth is triumphant even if intense. The flood of sensations and emotions parents feel may mean that the next stage, delivery of the placenta, is momentarily forgotten. After a baby is born, contractions continue and the placenta is released from the wall of the uterus, where it was transferring oxygenated blood and nutrients from mother to fetus via the umbilical cord.
Immediate postpartum contractions help shrink the uterus down to a smaller size, helping to deliver the placenta and close off blood vessels, which prevents bleeding. Some providers may offer uterine massage (which can be unpleasant but helpful), or prophylactic Pitocin to aid this process - especially if the circumstances of birth or the bright lights and unfamiliar experiences of a clinical setting interrupt the spontaneous process. The placenta usually delivers about 5 to 35 minutes after the baby arrives, and is aided by the hormones that are stimulated by skin-to-skin contact with the newborn, a calm, warm, quiet environment, and even a newborn’s first latches and suckling at the breast.
Whether or not the placenta has been delivered, until the umbilical cord is manipulated or clamped, it will continue to pump as much as 30% or more of the infant’s blood supply (including iron rich red blood cells and precious stem cells) back to the baby from the placenta. You can learn more about “delayed cord clamping” here.
After childbirth, many birthing people feel joy, relief, and fatigue. Some aftercare may be required to confirm the birthing person is safe and able to heal comfortably. Skin-to-skin contact between the birthing parent and their baby helps both of them to recover physically and hormonally.
Most babies are ready to nurse within a short period after birth, and show this through rooting instincts such as sniffing for the breast and sticking their tongue out. If you are planning to feed your newborn with human milk, practicing nursing from the start is recommended, as it helps both parent and baby to master this instinctual, but learned behavior. Allowing your baby to latch and suckle also helps the uterus to contract and prevents bleeding.
Even just a small amount of special early milk called “colostrum” will satisfy the newborn, whose stomach is only the size of a pea. Early feeding is motivated more by instinct than by hunger, as the newborn has been receiving nutrients from the placenta up through delivery, but these early feedings lay the pathways for future milk supply. This early bonding period also creates a foundation for the baby’s positive social interactions and brain development, and is supportive of postpartum emotional health in adults. Warmth, rest, and nourishment are key to parental and infant recovery.
We’ve described the physiological stages of labor and some of the experiences associated with each. Context, support and preparation matters, and the outcomes - both clinical and experiential - of any birth experience are shaped by the attitudes, relationships and communication between the birthing person and their team. How has your perspective on labor shifted as you’ve read this article?
If learning about the stages of labor helped put you at ease, you may want to dive into more learning about labor preparation, options for natural or medicated birth, and many other topics of education offered to expectant families who work with Seven Starling.
Hearing other people’s stories can also be a great tool for understanding birth, because no one story is exactly the same, despite these universal elements of physiological birth. If you felt anxious or learned something about labor that sparked a concerning question, it may be helpful to talk to other pregnant and birthing people or work with a doula. Learning more may help you discern between the primal, normal fears of new parenthood, and the worries and doubts that can come up due to misinformation, negative attitudes of the people around us, or previous challenging medical experiences.
We invite you to prepare for labor by reflecting on what helps you to feel most capable, and reaching out for more learning and support. Here at Seven Starling, we aim to offer versatile tools for every birthing person, with small group social support, holistic guidance from birth professionals, and an evidence-based, OB-approved curriculum that covers this topic and many many more, plus exercises and worksheets for planning your family’s new arrival with confidence and clarity.