Pregnancy involves profound physical transformations, and noticing that the rib cage seems wider or more “flared” after childbirth is a common concern. This change is a normal, expected physiological accommodation the body makes to nurture a growing baby. Understanding the mechanics behind this change, and what to realistically expect following delivery, can help alleviate worry. While recovery takes time, many of the changes involving the rib cage are temporary.
The Mechanism of Rib Cage Expansion
The primary reason for the widening of the rib cage during pregnancy is simple physics: the need for space. As the uterus expands to accommodate the developing fetus, the abdominal organs are displaced upward and outward. This upward pressure pushes against the diaphragm, the large muscle responsible for breathing, forcing the ribs to open to create more volume in the torso.
This physical displacement is assisted by the hormone relaxin, which is produced during pregnancy to soften ligaments and connective tissues throughout the body. Relaxin specifically targets the costal cartilage, the flexible connection point between the ribs and the sternum, or breastbone. The softening of this cartilage allows the rib cage to expand by an average of about two to three inches in circumference, adapting to the increased internal pressure and volume requirements. This expansion allows for the necessary increase in lung capacity, ensuring both mother and baby receive sufficient oxygen.
The Postpartum Reality: Defining “Going Back”
The question of whether ribs “go back to normal” depends on how the term is defined, as recovery involves both soft tissue and skeletal components. The costal cartilage, made pliable by relaxin, will begin to firm up and contract after hormone levels drop following delivery. This gradual tightening helps the rib cage diameter reduce significantly from its peak pregnancy width.
Studies suggest that for many women, a complete return to the pre-pregnancy width may not occur. A slight, permanent widening of the rib cage, often measuring one to two centimeters, is considered a common residual change. This subtle difference is a lasting imprint of the body’s structural achievement during pregnancy and is not a functional concern.
It is important to distinguish between this slight permanent structural widening and a condition known as “rib flaring.” True rib flaring is a postural issue where the bottom edge of the ribs sticks out or lifts upward, creating a noticeable angle. This flaring is less about the bones themselves and more about the engagement and function of the deep core muscles and the diaphragm.
Timeline and Influencing Factors in Recovery
The initial phase of rib recovery is closely tied to the dissipation of relaxin, which begins to decline immediately after birth. The highest levels of relaxin are generally out of the system within the first six to twelve weeks postpartum, allowing the softened ligaments and cartilage to stabilize and regain tension. During this initial period, many women notice that their rib cage circumference starts to decrease rapidly.
Full tissue recovery and the reconditioning of surrounding muscles take much longer, often extending up to six to nine months postpartum. Factors such as breastfeeding can influence this timeline, as relaxin may remain in the system longer for those who are nursing. Subsequent pregnancies also play a role, as the cumulative effect can lead to greater or more persistent widening. Pre-pregnancy posture and core strength also affect the speed of recovery, as a strong core helps the ribs return to a neutral alignment more quickly.
Addressing Persistent Posture and Core Issues
If the ribs still appear wide or flared several months after delivery, the issue is often related to the function of the deep core, rather than the skeletal structure. The deep core muscles, particularly the transverse abdominis, are responsible for stabilizing the torso and pulling the ribs downward and inward upon exhalation. If these muscles are weakened or have not been effectively reactivated, they cannot maintain a neutral rib position.
This persistent flaring is frequently linked to Diastasis Recti, the separation of the outermost abdominal muscles. When the core system is compromised, the internal pressure pushes outward, forcing the ribs to stay in an expanded, flared position. This poor alignment can also lead to back pain and pelvic floor dysfunction because the diaphragm, core, and pelvic floor muscles are designed to work together as a synchronized pressure system.
Focusing on proper breathing mechanics, specifically deep diaphragmatic breathing that expands the back and sides of the ribs, helps to restore this core coordination. If rib flaring or associated discomfort persists past the six-month mark, seeking guidance from a pelvic floor physical therapist is recommended. These specialists can provide targeted exercises to reconnect the deep core and diaphragm, which is often the missing step in guiding the rib cage back toward its pre-pregnancy alignment.