Lying on your back to give birth is not a biological necessity. It is a cultural habit that took root in Western medicine only a few centuries ago, driven largely by the convenience of doctors rather than the comfort or safety of mothers. For most of human history, and across most cultures worldwide, women delivered in upright positions: squatting, kneeling, sitting on birth stools, or standing. The shift to the recumbent position is a surprisingly recent story, tangled up with forceps, anesthesia, hospital beds, and a king’s voyeurism.
How Lying Down Became the Default
Until roughly the mid-seventeenth century, upright birthing positions were the norm almost everywhere. The change began when male physicians started replacing midwives in the delivery room across parts of Western Europe. The recumbent position made it easier for doctors to perform forceps deliveries, and the medical profession increasingly favored it for that reason.1Journal of Nurse-Midwifery. Position during labor and delivery: History and perspective One colorful origin story holds that King Louis XIV of France, who reigned from 1638 to 1715, wanted to watch his mistress give birth and insisted she lie flat so he could observe. When the midwives, unaccustomed to delivering in that position, ran into trouble, physicians were called in, and the practice gained credibility by association with medical authority.2PubMed Central. Inviting Newton to Visit the Delivery Room. The Role of Gravity During Childbirth
The practice solidified further in the nineteenth century when ether became a common anesthetic. Women turned onto their sides or backs to make anesthesia administration easier, and from that point forward, whatever position best suited the doctor’s workflow became the standard across Western Europe and North America.1Journal of Nurse-Midwifery. Position during labor and delivery: History and perspective By the twentieth century, hospital birth had become the norm in industrialized countries, and hospital beds were designed for a patient to lie in them. The lithotomy position, with a woman on her back and her feet in stirrups, became so standard that many people assumed it was the medically optimal way to deliver. It was not chosen for that reason.
What Lying Down Does to the Pelvis
The human pelvis is not a rigid structure. The bony dimensions of the birth canal shift depending on what position you are in, and those shifts matter during delivery. MRI measurements of women in different positions have found that squatting and hands-and-knees positions significantly widen key pelvic openings compared with lying on the back. In particular, the distance between the ischial spines, one of the narrowest parts of the birth canal, expanded by roughly half a centimeter in upright positions. The pelvic outlet also grew modestly wider in squatting and hands-and-knees postures.3PubMed. MR obstetric pelvimetry: effect of birthing position on pelvic bony dimensions Computational modeling of the pelvis during squatting has confirmed these measurements, with simulations matching the MRI data closely.4PubMed. Development and validation of a computational model for understanding the effects of an upright birthing position on the female pelvis
Half a centimeter may not sound like much, but in childbirth, where a baby’s head must navigate a tight passage, every fraction counts. And the issue is not just space. When you are upright, gravity pulls the baby downward through the pelvis. When you lie on your back, the baby’s presenting part has to travel partly against gravity, and clinicians regularly observe the baby’s head sliding back between contractions.2PubMed Central. Inviting Newton to Visit the Delivery Room. The Role of Gravity During Childbirth In upright positions, the force of gravity works with contractions rather than against them, which researchers believe helps dilate the birth canal more gradually and reduces the time the baby spends in the second stage of labor.
Blood Flow and the Problem of a Heavy Uterus
Position during labor affects more than the shape of the pelvis. A full-term uterus weighs several kilograms and, when a woman lies flat on her back, it presses directly onto the inferior vena cava, the large vein that returns blood from the lower body to the heart. MRI studies have shown that supine positioning compresses that vein, reducing both its height and the flow through it.5PubMed. The effect of maternal position on venous return for pregnant women during MRI The body compensates to some degree by routing blood through a backup pathway along the spine, and for most women this keeps things stable. But the overall effect is a drop in cardiac output and in the amount of oxygen-rich blood reaching the uterus and lower body when compared with lying on the side.6PubMed. Feasibility of MRI assessment of maternal-fetal oxygen transport and consumption relative to maternal position in healthy late gestational pregnancies
In healthy pregnancies, the fetus seems to tolerate this well. One MRI study found that while the mother’s cardiac output and uterine blood flow were lower in the supine position, the actual oxygen consumption of the fetus and placenta did not change between supine and lateral positions.6PubMed. Feasibility of MRI assessment of maternal-fetal oxygen transport and consumption relative to maternal position in healthy late gestational pregnancies So the worry is less about an immediate crisis and more about a general physiological disadvantage. Lying flat asks the cardiovascular system to work harder for the same result, especially during a process as physically demanding as labor. For some women, the compression can cause supine hypotension, a sudden drop in blood pressure that leads to dizziness, nausea, and fetal heart rate changes.
Does Position Change How Long Labor Takes?
Several trials have looked at whether upright positions actually shorten the pushing stage of labor. The evidence is reasonably consistent for women who do not have epidural anesthesia: upright positions tend to reduce the time it takes to deliver. In one trial, women who squatted using support bars during the second stage had a significantly shorter pushing phase and reported less pain than women placed in a semi-reclined position.7PubMed. The influence of different maternal pushing positions on birth outcomes at the second stage of labor in nulliparous women Another randomized trial found that squatting with ankle supports shortened the time from the start of pushing to birth by roughly 25 minutes compared with the semirecumbent group, and the squatting group reported lower pain scores on two different scales.8Journal of Nursing Research. Efficacy of an Ergonomic Ankle Support Aid for Squatting Position in Improving Pushing Skills and Birth Outcomes During the Second Stage of Labor
Those are meaningful differences. But the picture changes when epidural anesthesia enters the equation, which brings us to one of the main reasons the lying-down position persists.
Epidurals, Monitors, and the Infrastructure of Hospital Birth
Epidural anesthesia is one of the strongest practical reasons women end up on their backs. An epidural blocks sensation and motor control in the lower body, making it difficult or impossible to squat, kneel, or even stand safely. When researchers have compared upright and recumbent positions specifically among women with epidurals, the advantages of upright positioning largely disappear. A Cochrane review of five trials found no clear difference between upright and recumbent positions in the rate of operative delivery, the duration of the second stage, or trauma to the birth canal among women with epidurals.9PubMed Central. Position in the second stage of labour for women with epidural anaesthesia This makes sense: when the muscles and nerves driving active pushing are numbed, and when standing is unsafe, the position’s mechanical advantages are partly neutralized.
Beyond epidurals, continuous electronic fetal monitoring keeps many women tethered to the bed. Traditional wired monitors physically restrict movement, and women report discomfort and reduced ability to change positions as a result.10PubMed. How does the use of continuous electronic fetal monitoring influence women’s experiences of labour? A systematic integrative review of the literature from high income countries Wireless telemetry monitors exist and do allow more movement. Studies have found that women using wireless monitors are more mobile and adopt more upright positions during labor.11PubMed. Experiences and outcomes on the use of telemetry to monitor the fetal heart during labour But many hospitals still use the older wired equipment, and the combination of continuous monitoring, IV lines, and epidural catheters creates a web of tubes and wires that effectively confines a woman to her bed.
There is also a workforce and training issue. Most obstetricians in Western countries trained exclusively on deliveries performed in lithotomy or semi-reclined positions. Catching a baby when the mother is squatting or on all fours requires a different set of skills and a different arrangement of the room. Delivery beds are engineered for the supine position, with stirrups and adjustable sections that assume the doctor is seated between the woman’s legs. Maternity care organizations have called for allowing low-risk women to move freely during labor, yet evidence suggests that roughly 60 percent of women are still denied that mobility in practice.12PubMed Central. Healthy Birth Practice #2: Walk, Move Around, and Change Positions Throughout Labor
Perineal Tears and Episiotomy
One concern that sometimes gets raised about upright birthing is whether it causes more tearing. The evidence here is genuinely mixed, and it depends on the specific position and the severity of the tear. A large network meta-analysis found no significant difference between upright and supine positions for first-degree, second-degree, or severe third- and fourth-degree tears.13PubMed Central. Maternal Positioning in the Second Stage of Labour and its Relationship with Perineal Trauma: A Systematic Review and Network Meta-Analysis When the researchers ranked individual positions by risk, squatting came out as lowest-risk for both second-degree and severe tears, while hands-and-knees ranked lowest-risk for episiotomy.
A Cochrane review focusing on women without epidurals found that upright positions were associated with fewer episiotomies but a possible slight increase in second-degree tears, with no difference in severe tears.14International Journal of Nursing Sciences. A review and comparison of common maternal positions during the second-stage of labor A study from China found that women who stayed in lateral (side-lying) positions throughout both phases of the second stage had higher rates of intact perineum and fewer episiotomies compared with women who switched to lithotomy for the active pushing phase.15PubMed. Comparison of perineal outcomes in Chinese women adopting lateral positions and lithotomy positions during the passive and active phases of the second stage of labour Similarly, a trial of hands-and-knees delivery found lower episiotomy rates and more intact perineums in the hands-and-knees group, with no difference in blood loss or neonatal outcomes.16International Journal of Nursing Sciences. Comparing maternal and neonatal outcomes between hands-and-knees delivery position and supine position
The overall picture is that tearing risk is not a strong argument for the supine position. If anything, certain non-supine positions may help protect the perineum, though the differences are modest and vary by study. When the second stage is prolonged or a quick delivery is needed, squatting or sitting may help; when the priority is minimizing lacerations, side-lying or hands-and-knees positions show some advantage.17PubMed Central. Alternative Birthing Positions Compared to the Conventional Position in the Second Stage of Labor: A Review
Why Choice Itself Matters
The question of which position is “best” sometimes obscures a more important finding: the position a woman chooses for herself tends to lead to a better experience than the position chosen for her by a clinician. A cross-sectional study of over 700 women found that satisfaction with childbirth was significantly higher when women selected their own birthing position compared with having one imposed on them. On a seven-point scale, self-selected positions averaged a satisfaction score of about 5.7, compared with roughly 4.7 for externally determined positions.18PubMed Central. Birthing positions and mother’s satisfaction with childbirth: a cross-sectional study on the relevance of self determination A follow-up study from a separate randomized trial echoed this, finding that an upright birth position may lead to greater childbirth satisfaction.19PubMed. Who decides the position for birth? A follow-up study of a randomised controlled trial
This is not a small thing. Birth satisfaction affects postpartum mental health, bonding with the baby, and a woman’s willingness to have future children. The sense of control and agency during labor shows up consistently in the research as one of the strongest predictors of a positive birth experience. When the default position is one imposed by hospital routine rather than one offered as a choice, even women who might have freely chosen to lie down lose that sense of control.
The Evolutionary Backdrop
Human birth is unusually difficult compared with that of other primates, and the anatomy behind that difficulty sheds some light on why position matters so much. The human pelvis is shaped by competing evolutionary pressures. Walking upright on two legs favors a narrower, more compact pelvis, while delivering a large-brained baby favors a wider one. The traditional explanation was that the pelvis represents a direct compromise between these two demands, but more recent research has complicated that story. Biomechanical studies suggest that a wider pelvis does not actually hurt walking efficiency much. Instead, the main constraint may be that the pelvis has to support the weight of the internal organs and a heavy fetus during a long pregnancy, and a narrow pelvic floor does that job better.20PubMed Central. Evolution of the human pelvis and obstructed labor: new explanations of an old obstetrical dilemma
Because of these constraints, the human birth canal is not a simple tube. The inlet at the top is wider from side to side, while the outlet at the bottom is wider from front to back. The baby typically rotates during delivery to fit through these differently shaped openings, a process unique to humans and known as rotational birth. Researchers have argued that this complex canal shape evolved precisely because upright posture limits how deep the pelvic inlet can be from front to back without increasing the curvature of the lower spine to dangerous levels.21PubMed Central. The evolution of pelvic canal shape and rotational birth in humans The human pelvis, in other words, is already working within very tight margins. Any position that reduces those margins further, such as lying flat, is working against an anatomy that was not designed with much room to spare.
What You Can Actually Do About It
If you are planning a hospital birth and want to avoid spending labor on your back, a few practical realities are worth knowing. First, ask about monitoring options early. Wireless fetal monitors allow you to walk, change positions, and use a birth ball while your baby’s heart rate is still being tracked.11PubMed. Experiences and outcomes on the use of telemetry to monitor the fetal heart during labour Not all hospitals stock them, and asking in advance gives you time to find one that does or to discuss intermittent monitoring as an alternative for low-risk labor.
Second, understand how an epidural changes your options. If you plan to use one, discuss with your anesthesiologist whether a lower-dose or “walking” epidural might preserve enough leg strength to allow upright or lateral positions. Some women retain enough sensation to kneel on the bed or lie on their sides, though full squatting is usually off the table. Third, talk to your provider about their experience with non-supine deliveries. A midwife or obstetrician who has routinely caught babies in various positions will be far more comfortable supporting your preferences than one who has only ever worked with a woman in stirrups.
Birth plans are imperfect documents, and emergencies sometimes require specific positions for safety. But the evidence is clear that for straightforward, low-risk labor, the supine position offers no medical advantage, was never adopted because it was better for mothers, and in several measurable ways makes the process harder than it needs to be. The fact that it remains the default in most Western hospitals says more about institutional inertia than about what the science supports.