Physiological Adaptations of Pregnancy and Postpartum
A Healthful Mission
BeFit-Mom's mission is to help all women stay fit and healthy during pregnancy and beyond. Science now acknowledges these goals as not only medically sound, but beneficial for both the mother-to-be and her developing baby. Data from clinical studies has shown that fit moms have better control over weight gain, easier labor, leaner, healthier babies and they bounce back faster from pregnancy and childbirth than do sedentary women. A full discussion of the value of exercise during pregnancy can be found on the Benefits of Exercise During Pregnancy page of this web site.
Knowledge Is Your Ally
Your body will undergo tremendous changes during your pregnancy and postpartum periods, changes that may at times cause concern. Leading obstetrician and pediatrician Dr. Barry Brazelton stresses that because the mother's mental state influences the health of her baby, it is crucial for her to a maintain calm, positive state of mind during pregnancy. Knowing with reasonable certainty how to manage these changes-while safely engaging in activities that enhance the health of you and your baby-can give you invaluable peace of mind.
Bodily Systems Impacted during Pregnancy
During pregnancy, your body produces special hormones that stimulate physical changes in virtually every part of your body. Knowledge about these biomechanical changes in your metabolism, cardiovascular excercise and musculoskeletal systems is your best ally in your mission to have the healthiest pregnancy possible.
The Cardiovascular System
During pregnancy, the woman's cardiovascular system expands to support the needs of the growing fetus. These changes include:
- Boosts your blood volume, the amount of blood circulating through your body, by 40% to 50%.
- Raises your resting heart rate by about 15 to 20 beats per minute (BPM) by the third trimester.
- Elevates cardiac output, or amount of blood pumped per minute.
- Increases stroke volume, the amount of oxygenated blood pumped in one heartbeat.
- Expands tidal volume, or the amount of air you take in per breath.
- Dilates and relaxes your blood vessels, thereby decreasing resting blood pressure, and aiding in circulation.
What Pregnancy Does to Your metabolism
- Boosts basal metabolism.
- Raises your core temperature slightly.
- Slightly elevates your insulin levels.
- Elevates your daily caloric needs by 300 calories by second trimester.
- Increases your protein and fluid requirements.
How Posture and Spine Alignment Change during Pregnancy
Though subtle, the postural changes of pregnancy have profound effects on many areas of your body. As the weight of your baby grows and the uterus expands, the pelvis tips to counterbalance the load. The pubic bone and tailbone move backward, thereby increasing the arch in your lower back. In fitness terminology, this is called an anterior tilt of the pelvis or a lordotic posture.
Because the spine is a dynamic structure, alignment changes in the pelvis have a ripple effect on the rest of the spine. The thorax, or upper back, increases its curve, which rounds the shoulders forward and collapses the chest. In response to the increased thoracic curve, the head to slides forward. Too much curve in the upper back vertebrae is referred to as a kyphotic posture. So during pregnancy, women experience a compound alignment problem; a kyphotic/lordotic posture, which augments all of the natural "S" curves of the spine.
These postural misalignments have a series of adverse effects including:
- Compression the vertebral discs
- Increased strain on the articular surfaces of the spine
- Reduction of lung capacity
- Loss of height
- Ligament strain
- System wide changes throughout your muscular system
As pregnancy advances, the ribcage also expands dramatically, providing needed additional space for the lungs as the uterus expands and fills the abdominal cavity.
Muscular Imbalances of Pregnancy
To compensate for these postural deviations, specific muscle groups must work harder to support the body in the upright position. Over time, these muscles shorten and become hypertonic, or chronically too tight. Opposing muscle groups need to work less to support the body, and weaken and atrophy, or become hypotonic. These postural and muscular changes tend to be self-reinforcing. As the belly expands, the postural deviations worsen, which in turn, further augment muscular imbalances.
However, you can prevent or lessen most of these conditions with a prenatal exercise program that focuses on counterbalancing these effects by:
- Stretching muscle groups that tend to over-tighten
- Strengthening muscle groups that tend to weaken
- Choosing core strength and stability exercises that incorporate the neutral spine position
Muscles that Tighten during Pregnancy
- The hip flexors, or iliopsoas
- The thighs, particularly the long muscle of the thigh, the rectus femoris
- Deep muscles of the lower back quadratus lumborum
- The pectorals; chest muscles
- The internal rotators and elevators of the shoulders: the rhomboids, levator scapulae, and the upper fibers of trapezius
Muscles that Weaken or are Over-Stretched during Pregnancy
- Buttocks; gluteals or hip extensors
- Hamstring muscles; back of the thigh
- Abdominal muscles*
- Mid and lower fibers of the trapezius in the upper back
- The external rotators of the shoulder
- Serratus anterior; Scapular depression:
- Neck flexors, frontal only
- Pelvic floor muscles
- Intercostals; ribcage muscles
Pregnancy's Impact on Connective Tissues and ligaments
Pregnancy hormones stimulate lengthening and laxity in the ligaments and other connective tissues, which allows the pelvic outlet to expand during labor and delivery. ligament laxity leaves joints more vulnerable to injury and the postural effects of:
- Joint laxity and dynamic instability throughout the body, particularly the ankle, knee, pubis, sacroiliac, spine, shoulders, and wrist.
- Increased risk of nerve compression, such as sciatica, thoracic outlet syndrome and carpal tunnel syndrome. See the Common Pregnancy and Postpartum Discomforts page of this web site for more information on Carpal Tunnel Syndrome.
- Increased risk of acute joint injuries, particularly at the ankle, knee, pelvis and spine.
- Abdominal Separation. See Diastasis Recti page of this web site for complete details.
- Lower back pain caused by laxity and/or continual strain of uterine ligaments.
This discussion has provided an overview of the physiological adaptations of pregnancy. We encourage you to consult other sections of this web site for further details on how to protect your body, and how to optimize your physical fitness during and after pregnancy.