Pregnancy does cause measurable changes to the pelvis, but the popular idea that childbirth permanently “widens your hips” blends two different things happening at once: temporary bone movement and longer-lasting soft-tissue changes. The pelvic bones shift apart during pregnancy under the influence of hormones, and the joint at the front of the pelvis widens noticeably. That bony separation largely reverses within weeks of delivery. The increase in hip circumference that many people notice afterward is driven mostly by changes in fat distribution and connective tissue rather than by the skeleton settling into a new, wider configuration. The full picture, though, is more interesting than either a simple “yes” or “no.”
What Happens to the Pelvis During Pregnancy
The pelvis is not a single bone. It is a ring made of several bones connected by joints and ligaments. The joint at the very front, the pubic symphysis, is a fibrocartilage disc that normally holds the two halves of the pelvis tightly together. During pregnancy, a hormone called relaxin, produced mainly by the ovaries, loosens that joint and the ligaments around the sacroiliac joints in the back of the pelvis. Relaxin levels peak during the first three months of pregnancy and again near delivery, and the hormone’s loosening effect on pelvic ligaments is strongest in that late-pregnancy window.1PubMed Central. Role of relaxin in peripartum pubic symphysis diastasis This is the body’s preparation for birth: the ring of bone needs a bit of give so a baby’s head can pass through.
Other mechanical forces contribute too. The growing uterus pushes outward against the abdominal wall and downward into the pelvis, imposing sustained pressure that, along with increased body weight and postural shifts, loads the pelvic ring differently than it was loaded before pregnancy.2PubMed Central. Sacroiliac Joint and Pelvic Dysfunction Due to Symphysiolysis in Postpartum Women Combined with the hormonal loosening, these forces mean the pelvis is genuinely a slightly different shape by the time delivery happens.
How Far the Bones Actually Move
The amount of bony movement is real but smaller than many people imagine. A study measuring the pubic symphysis in 91 women immediately after delivery found an average separation of about 7.6 mm. Importantly, the method of delivery did not make much difference: women who delivered vaginally averaged about 7.2 mm and those who had cesarean sections averaged about 8 mm, a gap that was not statistically significant. By six weeks postpartum, the pubic symphysis had returned to a normal width of 4 to 5 mm in most women.3PubMed. Pubic Symphysis Separation and Regression in Vaginal versus Cesarean Delivery So the bones do move apart, but the body pulls them back together fairly quickly once pregnancy hormones drop.
Birthing position can nudge the symphysis a bit wider in the moment. Ultrasound measurements of pregnant women in different positions found that standing, squatting, and lithotomy positions widened the symphysis by roughly a millimeter compared to lying flat on the back, though the sample was small and no firm conclusions could be drawn.4PubMed. Measurement of pubic symphysis width in different birthing positions using ultrasound These are short-lived positional effects, not permanent changes.
Body composition and race appear to matter. The same study that measured postpartum symphysis width found that Black race and obesity were both associated with greater separation.3PubMed. Pubic Symphysis Separation and Regression in Vaginal versus Cesarean Delivery This kind of individual variation is a recurring theme throughout pelvic research: the human birth canal is highly variable in shape, both within and among populations, and those shape differences affect how labor unfolds.5PubMed Central. Shaping birth: variation in the birth canal and the importance of inclusive obstetric care
Why Your Hips Still Look Wider After Baby
If the bones go back, why do so many people feel their hips are permanently wider? The answer is mostly fat and connective tissue. A longitudinal study following adolescents and young women over a decade found that those who had given birth gained substantially more hip circumference than those who had never been pregnant. Among Black women who had one birth, hip circumference increased by about 2 cm more than in women who had not been pregnant, even after accounting for age, income, baseline measurements, and other variables. Women who had given birth more than once saw an even larger difference, around 4 cm.6PubMed Central. Longitudinal study of growth and adiposity in parous compared with nulligravid adolescents These women also gained more in waist circumference, overall weight, and body fat percentage, pointing to a broad shift in body composition rather than a change in skeletal width.
Pregnancy redirects where the body stores fat. During pregnancy and the postpartum period, waist and hip circumferences both increase, and not all of that added tissue disappears afterward.7British Journal of Nutrition. A longitudinal study of maternal anthropometric changes in normal weight, overweight and obese women during pregnancy and postpartum When you wrap a tape measure around wider hips six months after delivery, what the tape is measuring is largely a change in the amount and location of adipose and connective tissue, not a skeleton that permanently expanded.
When the Widening Goes Too Far
In rare cases the pubic symphysis does separate more than it should. A gap wider than 10 mm is clinically defined as pubic symphysis diastasis and is considered a complication of vaginal delivery or pregnancy.8PubMed Central. Postpartum pubic symphysis diastasis-conservative and surgical treatment methods, incidence of complications Most women with mild-to-moderate diastasis recover with conservative treatment: bed rest, a pelvic binder, physical therapy, and pain management. When the gap exceeds about 4 cm, though, the symphyseal ligaments are usually torn along with damage to the sacroiliac joint capsule, and surgery may be needed to stabilize the pelvis. Surgical repair tends to speed up the ability to walk again and lowers the risk of chronic pain and joint scarring.9PubMed Central. Postpartum Pubic Diastasis with Significant Widening: A Rare Case Series
These extreme cases are uncommon. In the 91-woman study mentioned earlier, 10 women had a separation between 10 and 15 mm, and the three widest gaps were all after vaginal deliveries.3PubMed. Pubic Symphysis Separation and Regression in Vaginal versus Cesarean Delivery Severe diastasis requiring intervention is rarer still, but anyone experiencing significant groin or pelvic pain after delivery that makes it hard to walk should bring it up with a provider rather than assuming it will resolve on its own.
Why the Human Pelvis Is So Rigid Compared to Other Mammals
One of the most interesting angles on this question comes from evolutionary biology. In many mammals whose newborns are proportionally as large as, or even larger than, human babies relative to the mother’s birth canal, the pubic symphysis opens widely during delivery. In guinea pigs, for instance, the joint can separate by centimeters. Humans cannot do this, and the reason appears to be a set of constraints imposed by walking upright. Bipedalism requires a pelvis that works as a stable, weight-bearing bridge between the spine and the legs, and a joint that swings wide open during birth would compromise that structural role.
Researchers have described this as a trade-off: a wider, more flexible birth canal would make delivery easier but would increase the risk of pelvic organ prolapse and incontinence by weakening pelvic floor support. Mathematical models suggest that the human pelvis has arrived at an evolutionary compromise that inevitably leaves some babies too large for some birth canals.10PubMed. Evolution of the human birth canal So the fact that human hips widen only a little during pregnancy, rather than dramatically, is not a design flaw. It is the pelvis doing its best to serve two competing jobs at once.
Hormones also shape the pelvis across a woman’s entire lifetime, not just during pregnancy. Research on pelvic development has shown that sex hormones drive the female pelvis to widen during puberty and maintain its shape into reproductive age, a process that amounts to developmental plasticity influenced by nutrition and ecology as well as genetics.11PubMed Central. Developmental evidence for obstetric adaptation of the human female pelvis In other words, some of the hip width you associate with womanhood was established hormonally well before any pregnancy occurred.
Age and Skeletal Maturity at First Birth
How old you are when you first give birth can affect how the pelvis responds. X-ray measurements comparing pregnant adolescents with adult women found that the majority of pelvic dimensions were significantly smaller in teens under 16, and several dimensions were contracted more frequently. The pattern suggested that the adolescent pelvis has not yet fully matured at that age. During puberty, the pelvis grows at an accelerated rate and typically shifts from a narrower to a rounder configuration, and giving birth before that process finishes means delivering through a pelvis that is still reaching its adult shape.12PubMed. X-ray pelvimetry of the pregnant adolescent. Pelvic size and the frequency of contraction
For younger mothers, the question of whether birth “widens” the hips gets tangled with the fact that their hips were already widening on their own developmental schedule. Separating the effect of pregnancy from the effect of continued growth becomes difficult, and it is possible that some of the lasting hip-width increase reported by young mothers is partly normal maturation that happened to coincide with pregnancy.
Your Feet Change Too
If you are looking for a skeletal change from pregnancy that is genuinely permanent, the pelvis is not the best example. Your feet are. A study tracking women before, during, and after their first pregnancy found that arch height and arch rigidity decreased significantly, while foot length increased. These changes persisted well after delivery and were most pronounced with the first pregnancy; subsequent pregnancies did not add much more flattening.13PubMed Central. Pregnancy leads to lasting changes in foot structure The likely mechanism is the same relaxin-driven loosening of ligaments that affects the pelvis, except the foot’s arch depends on those ligaments for structural support and apparently does not fully recover once they stretch.
This finding surprises many people who assumed their bigger shoe size after pregnancy was just swelling that never went away. It is structural: the arch drops, the foot elongates, and it stays that way. Some women go up half a shoe size permanently. Meanwhile, the pelvis, which gets far more attention in the “did birth change my body?” conversation, largely snaps back.
Postpartum Movement and Recovery
Even though the pubic symphysis typically normalizes within weeks, the broader musculoskeletal system takes longer to settle. Abdominal muscles stretch and thin during pregnancy as the uterus expands, and the separation of the rectus abdominis muscles along the midline, called diastasis recti, is extremely common.14PubMed Central. Diastasis recti abdominis: A comprehensive review The loosened pelvic floor, shifted center of gravity, and weakened core all contribute to changes in how people move. Postpartum runners, for example, show restricted rotation in the pelvis and trunk compared to their pre-pregnancy running gait, along with wider steps and longer time spent on each foot during stance.15Wolters Kluwer / Ovid. Restriction in Pelvis and Trunk Motion in Postpartum Runners Compared With Pre-pregnancy These gait changes persist even when people feel otherwise recovered, suggesting that the body compensates for lingering instability in the pelvis.
Stabilization exercises that target the deep core and pelvic floor muscles are the best-supported intervention for postpartum pelvic pain. A meta-analysis of randomized trials found that these exercises significantly reduced both pain and disability in women with lumbopelvic pain after delivery, with strong short-term evidence.16PubMed Central. Effectiveness of physical therapy on pain, disability and quality of life in women with lumbopelvic pain in postpartum period A separate randomized trial found that stabilization exercises improved pelvic floor and deep abdominal muscle function more effectively than general exercise in women with postpartum lumbopelvic pain.17PubMed. Stabilization exercise affects function of transverse abdominis and pelvic floor muscles in women with postpartum lumbo-pelvic pain Another systematic review and meta-analysis of randomized trials confirmed that stabilizing exercises targeting the lumbopelvic region significantly reduced both pain and disability in postpartum women.18PubMed. A Systematic Review and Meta-analysis of Randomized Controlled Trials of Stabilizing Exercises for Lumbopelvic Region Impact in Postpartum Women With Low Back and Pelvic Pain
The practical takeaway is that the feeling of “wider hips” or general instability in the pelvis after birth often reflects muscle weakness and connective tissue laxity that is very responsive to targeted exercise, not a permanent change in the skeleton that you are stuck with.
Connective Tissue Variation and Individual Response
Not everyone’s connective tissue responds to pregnancy the same way. Some people are naturally more flexible in their joints, a trait called hypermobility, and you might expect that to make a big difference in how the pelvis behaves during birth. A study of nearly 600 women found that about 8% had hypermobility, and those women had lower odds of needing an operative vaginal delivery or cesarean after full dilation and were less likely to experience severe tearing. However, hypermobility was not associated with any pelvic floor disorder afterward.19PubMed Central. Joint hypermobility, obstetrical outcomes, and pelvic floor disorders In other words, having naturally loose ligaments may make delivery a bit easier mechanically without necessarily causing worse long-term pelvic consequences. This counters the intuition that more flexible connective tissue would lead to more postpartum pelvic instability.
Parity and Long-Term Joint Health
A question many people do not think to ask is whether repeated pregnancies affect joint health over the long run. The evidence here is mixed but worth knowing about. A large Danish study of over 4.6 million people found that women with children had a modestly higher risk of osteoarthritis of the knee, back, and hand compared to women without children, but there was no increased risk for hip osteoarthritis.20PubMed. Socio-demographic factors, reproductive history and risk of osteoarthritis in a cohort of 4.6 million Danish women and men Interestingly, men with children showed the same pattern, raising the possibility that something about the parenting lifestyle, not pregnancy itself, drives part of the association.
A Korean study added a wrinkle. It found that vaginal delivery was linked to higher odds of symptomatic back osteoarthritis compared to cesarean delivery, but vaginal delivery was actually associated with lower odds of radiographic hip osteoarthritis.21PubMed. The associations between parity, other reproductive factors, and osteoarthritis in women aged over 50 years A more recent retrospective analysis found a dose-response relationship between number of births and osteoarthritis severity in elderly women: among women who had given birth many times, nearly a quarter had the most severe grade of osteoarthritis, compared to under 6% of women who had never given birth.22PubMed Central. Correlation between Parity and Risk of Osteoarthritis in Elderly Women: A Retrospective Analysis
These findings do not prove that pregnancy destroys joints, and they cannot fully separate the effects of pregnancy from the effects of decades of physical labor, weight changes, and other confounders. But they do suggest that the cumulative musculoskeletal toll of multiple pregnancies, including the repeated hormonal loosening and weight-bearing stress, is not trivial and may show up decades later in ways that have nothing to do with hip width.