The question of whether a woman’s hips widen during pregnancy is one of the most common physical inquiries expectant mothers have. The answer is complex, involving temporary biological mechanisms that cause skeletal joint movement and external factors that contribute to the appearance of increased width. These changes are a natural part of the body’s preparation for childbirth, but their extent and duration vary significantly among individuals.
The Hormonal Trigger: Relaxin and Joint Softening
The primary physiological driver behind pelvic changes is the hormone Relaxin, a substance produced by the ovaries and the placenta. Relaxin begins to circulate in the body early on, often peaking near the end of the first trimester, though its presence continues throughout the entire pregnancy.
The function of this hormone is clearly indicated by its name, as it works to soften and relax the body’s connective tissues, including ligaments, tendons, and cartilage. While this effect is systemic, it is particularly focused on the pelvic region to allow the rigid framework of the pelvis to become more flexible. This increased flexibility is a necessary biological adaptation, making space for the growing fetus and preparing the birth canal for delivery.
Anatomical Shifts in the Pelvic Girdle
The softening effect of Relaxin is concentrated on the three main joints of the pelvic girdle. These are the two sacroiliac joints, which connect the back of the pelvis to the lower spine, and the pubic symphysis, the cartilaginous joint linking the two halves of the pelvis at the front. The movement at these joints is what constitutes the actual widening of the skeletal structure.
The pubic symphysis, which typically measures about 4 to 5 millimeters in width in non-pregnant women, can increase to 6 to 8 millimeters or more during pregnancy. This widening is a gradual process that often peaks in the third trimester as the body adapts to the increasing size and descent of the baby. While this increase in separation is minimal in millimetres, it represents a significant change in the body’s biomechanics and is crucial for facilitating the passage of the baby during delivery.
Differentiating Structural Change from Appearance
The perception of “wider hips” is often amplified by factors that are not related to the skeletal movement itself. A large part of a woman’s apparent increase in size around the hips and thighs is due to natural gestational weight gain. This gain includes fat deposition in the lower body, which is a common and healthy way for the body to store energy reserves for the later stages of pregnancy and breastfeeding.
Increased water retention and swelling, or edema, particularly in the lower extremities, also contribute to a broader appearance. Furthermore, the body’s center of gravity shifts forward to accommodate the growing uterus, which causes many women to instinctively change their posture. This change often involves an increased anterior tilt of the pelvis and a deepening of the natural curve in the lower back, known as lordosis, which can make the hips appear more prominent or wider than they structurally are.
Postpartum Resolution: Are the Changes Permanent?
The physical changes brought on by pregnancy are largely temporary, though full recovery requires time and varies per person. After delivery, the levels of Relaxin drop significantly, which signals the ligaments and connective tissues to gradually begin tightening again. This process allows the pubic symphysis and sacroiliac joints to stabilize and return closer to their pre-pregnancy position.
The timeline for this stabilization is not immediate; while the uterus shrinks back relatively quickly, the full restoration of connective tissue strength can take many months. It is common for Relaxin levels to remain elevated for several months postpartum, sometimes up to 12 weeks, and potentially longer for women who are breastfeeding.
For most women, the skeletal changes largely resolve, but a slight, lasting increase in pelvic dimension or a permanent shift in the pelvis’s resting position is possible. This minimal permanent repositioning, combined with any residual weight gained during pregnancy, can result in an enduring change to the overall body shape, sometimes leading to a lasting increase in perceived hip width or clothing size.