SPORTS AND PREGNANCY (I): PHYSIOLOGICAL EFFECTS

This is the first part of a monographic about sports and pregnancy. In this entry we are going to explain the main effects of exercise on women and foetus, and what are the actual recommendations. In the next one we will focus specifically in running women.

Firstly, we can distinguish two categories of pregnant women:

  • Previously sedentary: recommend gradual progression of exercise beginning with walking program.
  • Previously active: no safe upper level of intensity established. Continue previous fitness routine if there is an uncomplicated pregnancy.

 

Physiological changes of pregnancy for women can be classified in:

Musculoskeletal

  • Weight gain
  • Shifted center of gravity
  • Increased ligamentous laxity

Cardiac

  • Increased blood volume: up to 50% at term
  • Increased heart rate: resting can increase 10-15 bpm
  • Increased stroke volume and cardiac output
  • Decreased systemic vascular resistance and blood pressure

Respiratory

  • Increased tidal volume and minute ventilation: up to 50%
  • Physiologic decrease of pulmonary reserve
  • Decreased oxygen availability

 

Exercise effects on the foetus:

  • Increased heart rate: 10 to 30 bpm over baseline during/immediately after exercise
  • No clinically significant difference in birth weight
  • Assessment of umbilical artery blood flow, heart rate and biophysical profile before/after 30 minutes of exercise showed that it was well tolerated
  • Better tolerance of labor process

 

Exercise effects on the mother:

  • Fitness improvement/maintenance
  • Decreased overall pregnancy weight gain
  • Decreased incidence of gestational diabetes mellitus (or improved blood glucose control in patients with it)
  • Reduced risk of preeclampsia (gestational high blood pressure)
  • Decreased rate of caesarean deliveries
  • Decreased labor and postpartum recovery times

Up to 40 min of moderate exercise is well tolerated by low-risk pregnant women.

 

Exercise general guidelines would be:

  • Ensure adequate hydration
  • Walking, strength training, and water exercises are safe for almost all women
  • Biking is safe during the first trimester but advised against as pregnancy progresses because of balance changes and fall risk
  • Avoid activities with high fall risk, high altitude, supine positions (some in yoga and Pilates) and scuba diving

 

Stop exercise if you observe:

  • Vaginal bleeding or leaking fluid
  • Regular contractions
  • Dyspnea, or breathing difficulty
  • Dizziness or Headache
  • Chest pain
  • Muscle weakness affecting balance
  • Calf pain or swelling

 

Contraindications to exercise:

  • Hemodynamically significant heart disease
  • Restrictive lung disease
  • Incompetent cervix/cerclage
  • Multiple gestation
  • Second/third trimester bleeding
  • Placenta previa (obstruction of the uterus by the placenta) after 26 wk of gestation
  • Premature rupture of membranes or labour
  • Preeclampsia (high arterial pressure)
  • Severe anaemia

In our next entry we are going to focus on running women, and how they tackle with training and the body and physical changes of pregnancy.

 

Bibliography:

Exercise During Pregnancy.

Albright E.

Curr Sports Med Rep. 2016 Jul-Aug;15(4):226-7. doi: 10.1249/JSR.0000000000000277.

Picture by Dan Evans (Pixabay)

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