Physiologic Changes in Pregnancy and How Physical Therapy Can Help

Physiologic Changes in Pregnancy and How Physical Therapy Can Help

Most systems of the body undergo change during the 9 months of pregnancy including the reproductive, cardiovascular, gastrointestinal, respiratory and endocrine system. The breasts and kidneys are also changing as well as the metabolic and dermatologic functions of the body.

Cardiovascular Changes:

Some of the cardiovascular changes during pregnancy are the following:

  • –blood volume increases approximately 50%
  • dilutional anemia occurs because of an initial early increase in plasma volume and a slower initial increase in red cell mass
  • pulse rate increases 10-15 beats/min
  • chambers of the heart dilate and the position of the heart changes, rotating outward and to the left
  • stroke volume and cardiac output increase 30% to 50%
  • blood pressure decreases slightly
  • venous return to the heart is affected by the increasing size of the uterus (especially in supine position)

In well conditioned athletes, blood flow to the uterus and heat dissipation may be improved with exercise because of increased blood volume, as compared to sedentary women

Respiratory Changes:

The overall vital capacity is unchanged; the diaphragm elevates and the ribs cage expands and flares; the residual volume decreases and the tidal volume/oxygen consumption increases. The respiratory changes that are occurring with the mother are amplified with the fetus. Therefore, if the mother is experiencing a persistent state of hypoxia or acidosis while exercising, the fetus will experience these respiratory changes to a greater degree. It is for this reason that prolonged anaerobic exercise (short exertion high intensity; ex. sprinting, weight lifting, jumping) is not recommended, or aerobic exercise that causes dyspnea.

Musculoskeletal Changes:

Posture, gait, balance are all affected. The center of gravity moves up and forward, causing flexion in the neck area and hyperextension in the lumbar spine. The hormones progesterone and relaxin increase ligamentous and joint laxity. The additional body weight increases the joint forces on the spine. There is an increased risk for sprains, strains, and falls. Active women may want to opt for swimming or low impact aerobics rather than running or physical sports.

What physical therapy techniques are contraindicated in pregnant patients

  •  Deep heat modalities and electrical stimulation
  •  Positions that:
    •  involves abdominal compression in mid to late pregnancy
    • maintain the supine position longer than 3 minutes after the 4th month of pregnancy
    • raise the buttocks higher than the chest
    • strain the pelvic floor and abdominal muscles
    • encourage vigorous stretching of hip adductors
    • involve rapid, uncontrolled bouncing or swinging movements

How is the pubic symphysis affected during pregnancy?

Changes begin as early as the tenth or twelfth week of pregnancy. Radiographic evidence has shown changes beginning during the first trimester with maximum relaxation at term. The hormone relaxin has been identified as the major contributor to this response. There is only pain if there is dysfunction within this joint or the pelvic ring. Rupture of the pubic symphysis associated with pregnancy is rare but can occur in late pregnancy or with delivery.

What causes back pain during pregnancy?

The hormone relaxin is released by the third month of pregnancy, and under its influence, increased movement is experienced throughout the vertebral spine and pelvis. Many pregnant women complain of low back pain, which often is caused by the many physical changes of pregnancy: added weight, increased lordosis, changes in the center of gravity, loose pelvic ligaments, and poor muscle tone. Back pain may be muscular, mechanical, joint or diskogenic in origin.

Following a normal vaginal delivery, how soon can women begin:

  • Pelvic floor exercises/Kegel exercise- This type of exercise should be initiated as soon as possible following a delivery. It can aid in healing, improve circulation to the perineal tissue, aid in reduction of urinary stress incontinence, and accelerate improvement in muscle tone for tissue that may be experiencing sudden onset of decreased tone and proprioception as a result of the trauma of delivery.
  • Aerobic exercise– This can be resumed as soon as the patient feels able. Hormone induced joint laxity can be present up to 4 – 6 weeks postpartum. If the mother is breast feeding, this could be longer. Therefore the patient should take precautions to protect joints by not stretching them beyond their physiologic ranges. Hamstrings and adductors should e stretched with caution because of their relationship with the pelvic girdle. The patient should be careful not to promote hypermobility and instability. Lower extremity unilateral weight bearing exercises can lead to sacroiliac and/or pubic symphysis pain.

How soon following a cesarean section can women begin physical therapy/exercises?

Pelvic floor exercises can begin as soon as the woman is comfortable. Abdominal exercises should not be performed for 6-8 weeks following surgery or until cleared by the physician, other than pelvic tilts and abdominal isolation exercises. Aerobic activity can begin with light conditioning when cleared by the surgeon. The activity should not apply unnecessary pull or tension on the abdominal wall incision

American College of Obstetrics and Gynecology Guidelines when treating a pregnant patient:

In the absence of other medical or obstetric condition/complication:

  • Perform 30 minutes (or more) of moderate exercise per day.
  • Avoid supine exercise after first trimester
  • Avoid prolonged periods of motionless standing
  • Do not exercise to fatigue/exhaustion
  • Non weight bearing exercises (eg: swimming, cycling) are recommended. Some weight bearing exercise can be continued during pregnancy if the exercise remains at the pre pregnancy intensity
  • Avoid exercise that can challenge balance or involve potential for even mild abdominal trauma
  • Pregnancy requires an additional 300kcal/day; therefore a woman who is exercising should ensure adequate caloric intake
  • Post partum exercise should resume gradually as tolerated by the woman’s physical capabilities

Contraindications to Exercise:

  • Pregnancy induced hypertension
  • Preterm rupture of membranes
  • Preterm labor during the prior or current pregnancy or both
  • Incompetent cervix or cerclage
  • Persistent second- or third trimester bleeding
  • Intrauterine growth retardation

Precaution (need to be cleared by physician):

  • Chronic Hypertension
  • Active thyroid, cardiac, vascular or pulmonary disease.


Orthopedic Physical Therapy Secrets 2nd Edition, Jeffrey D. Placzek, MD PT, David A. Boyce, PT, EdD, OCS, pp 230-233

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