Worldwide, physical inactivity is the fourth-leading risk factor for early mortality.The new American College of Obstetrics and Gynecology (ACOG) stresses the positive contribution of exercise during pregnancy.

The American College of Obstetricians and Gynecologists (ACOG) has reaffirmed its committee opinion in 2017 regarding physical activity and exercise during pregnancy and the postpartum period, based on the emerging clinical and scientific advances.Physical inactivity leading to weight gain during pregnancy is one of the major factors for maternal obesity and related complications such as gestational diabetes mellitus (GDM) and high blood pressure. For healthy individuals with uncomplicated pregnancies, physical activity should be encouraged as it is desirable and safe. However, in complicated cases, the physician should individually evaluate the women for their medical and obstetric complications and advise accordingly. In such cases, utmost care needs to be taken as the risk of complications such as miscarriage, poor fetal growth, musculoskeletal injury, and premature delivery, may be high.

Recommendations

Aerobic and strength-training exercises may be advised to women with uncomplicated pregnancies, before, during, and after pregnancy.Care should be taken to avoid sport-related musculoskeletal injuries and joint laxity. The following points should be pondered over before recommending physical activities to pregnant women:

• Due to anatomic and physiological changes, forces across joints and spine may increase with weight-bearing exercises, as a result of which about 60% pregnant women experience lower-back pain. Exercises which help in strengthening the abdominal and back muscles should be advised.
• Systemic vascular resistance decreases, while there is an increase in blood volume, heart rate, stroke volume, and cardiac output in pregnant women. These hemodynamic changes establish the circulatory reserve that is needed.
• Activities that may result in decreased venous return and hypotension, such as, motionless yoga, should be discouraged.
• Decreased subjective workload and maximum exercise performance are seen in pregnant women, mostly obese or overweight women, which limits their ability to engage in the strenuous physical activity. This is due to the decrease in the pulmonary reserve and increase in minute ventilation up to 50%.
• Aerobic training may increase the aerobic capacity in normal and overweight/obese pregnant women.
• During exercise, pregnant women should stay well-hydrated, wear loose-fitting clothes, and avoid high heat and humidity. Body temperature regulation is dependent on hydration and environmental conditions. Increased body temperature may pose a risk of neural tube defect, however, exercising does not increase the core body temperature into the range of concern.
   

Fetal Response to Maternal Exercise

Fetal heart rate changes and birth weight in relation to maternal exercise have been studied in detail. A minimum-to moderate increase in the fetal heart rate has been demonstrated, which is 10-30 beats per minute above baseline. The difference in birth weight has been seen as minimum or none when compared with controls.A cohort study demonstrated that 30 minutes of strenuous exercise in the second trimester was well tolerated in active as well as inactive pregnant women. The study assessed the umbilical artery blood flow, fetal heart rates, and biophysical profiles before and after the exercise.

Recommending an Exercise Program

Motivational Counseling

The likelihood for behavioral change and adaptability increases during pregnancy due to increased motivation and constant access to medical care. Patients make an effort to control weight, improve physical activity and diet as suggested by the physician. Motivational tools such as five A’s (Ask, Advise, Assess, Assist, and Arrange) have been successfully used for exercise and diet counseling.

Prescribing an Individualized Exercise program

• A minimum of 20-30 minutes of physical activity of moderate intensity every day, should be encouraged.
• Before recommending an exercise regime, the physician needs to ensure that the patient does not have a reason to avoid exercise and this can be done by a thorough clinical evaluation. The regime should be customized for each patient.
• Examples of safe activities are walking, swimming, stationary cycling, low-impact aerobics, modified-yoga, modified-pilates, running or jogging, racquet sports, and strength training.
• Examples of unsafe activities are contact sports such as ice hockey; baseball; boxing; soccer, activities with high risk of falling, scuba diving, skydiving, hot pilates, etc.
• The use of ratings of perceived exertion is more effective means to monitor heart rate as there may be blunted heart rate responses during exercise in pregnancy.
• Staying hydrated, avoiding lying on back for longer periods, and being alert regarding warning signs should be advised.
• Pregnant women who were sedentary before pregnancy should follow a gradual progression of exercise regime and women who were regular exercisers before pregnancy may engage in high-intensity exercise programs such as jogging, aerobics, etc. High-intensity and exercise exceeding 45 minutes may lead to hypoglycemia. Therefore, it is advisable to limit the exercise session or increase calorie intake before exercising.
• Exercise should be performed in thermoneutral or controlled environment conditions with attention paid to proper hydration and calorie intake.
• Physical activity and dehydration during pregnancy may result in minor uterine contractions, however, it may not be a cause for concern.
• Recreational Activities
• Participation in a wide range of safe activities should be considered. Sports which may result in abdominal trauma, scuba diving, skydiving, and activities with a high risk of falling should be avoided.

Special Populations

• Physical activities including judicious diets should be encouraged for obese women and exercise should start with low-intensity for short periods and be increased gradually.
• Athletes would require closer supervision as their workout regime is intense and they resume to high-intensity postpartum training sooner than others. Special attention should be paid to avoid hyperthermia, maintaining hydration, and adequate calorie intake which may adversely affect fetal growth.

Reference: ACOG Committee Opinion on Physical Activity and Exercise during Pregnancy and the Postpartum Period