Exercise and pregnancy

Question 1

Are babies born to active mothers any smaller?

Answer 1

Many types of maternal non-weight-bearing and weight-bearing exercise have been studied during pregnancy and none appear to increase the risk of an abnormal short-term outcome.

Question 2

What effect does post-partum exercise have on reducing body fat % in mothers?

Answer 2

o Results of studies performed on breastfeeding women suggest that exercise improves aerobic fitness, plasma lipids and insulin response.
o However, exercise alone without calorie restriction does not promote weight loss.
o Once lactation is established, overweight women may restrict energy intake by 500kcal/d to promote a weight loss of 0.5kg/wk without affecting infant growth

Question 3

What is the effect of exercise on the quality of breast milk?

Answer 3

Moderate exercise does not affect immunological component concentrations (sIgA, lactoferrin and lysozyme), vitamin B6, or essential fatty acids in breast milk.

Question 4

Is the normal growth and development negatively affected in children whose mothers were active during pregnancy?

Answer 4

Long-term follow-up data are quite limited, but it appears that beginning or continuing weight-bearing types of exercise during pregnancy has no adverse effects on postnatal growth, health or neurodevelopment

Question 5

Why might exercise prevent preeclampsia?

Answer 5

o Reduced levels of C-reactive protein
 C reactive protein stops endothelium producing NO, thus less vasodilation
o Increased nitric oxide production by endothelium = vasodilation
o Decreased Leptin
 Leptin may contribute to hypertension because of its role in stimulating the body to burn fat. Leptin stimulates SNS activity to burn fat – but this increases blood pressure and lead to hypertension

Question 6

Does being fit help labour?

Answer 6

o Minimal research evidence
 Some evidence to support reduced length of labour and complications Inconclusive evidence
o Hypothetically
 Higher VO2 should allow female to cope better with O2 demand of labour
 Training induced enhancements in beta-endorphins may help

Question 7

What are the cardiovascular changes during pregnancy?

Answer 7

o The heart adapts to the increased demands placed on it by the enlarging uterus and growing foetus
o ↑ cardiac output 30% to 50%
o Resting heart rate ↑ 25%
 5-10 bts.min-1 in the first trimester
 15 bts.min-1 in the second and third trimesters
• Increased oestrogen and human chorionic gonadotropin stimulates HR increase
• Sympathetic nervous system activation secondary to maintaining BP
o Oestrogen / progesterone reduce peripheral vascular resistance by 20%, thus HR must increase to maintain BP
o Stroke volume ↑ 25%
 ↑ blood volume
• Progesterone increases production of Renin by kidney Sodium reabsorbed Kidneys reabsorb fluid to expand plasma volume
• Increased EDV
 Increased LV size due to maternal hormones
• Oestrogen stimulates myocardial hypertrophy and increased contractility
• Increased blood volume stimulates some myocardial hypertrophy
• Growth is eccentric rather than concentric
 Reduction in peripheral vascular resistance
 10% growth in SV even by 1st trimester
o ↑ in blood volume - 35% to 50%
 Blood pressure - Increased volume offset by an increase in venous capacitance = blood pressure is not increased
• Problems with postural hypotension
 ↑ vasodilation at the skin, increases heat loss - help to prevent hyperthermia during exercise
 Anaemia
• results from a relatively greater increase in plasma volume than red cell mass (only ↑ 20%)
• Hb 150g.L-1 pre-pregnancy to 120g.L-1 in 3rd trimester
 White cell production also increased
o Blood clotting risk may increase and there will be a tendency to develop varicose veins
 Relaxation of the blood vessel walls with hormonal changes (to keep BP normal after ↑ in blood volume) and from the pressure of the uterus on the inferior vena cava
 Exercise assists blood flow in the legs and feet and helps prevent or minimize these problems.

Question 8

What are the pulmonary changes during pregnancy?

Answer 8

o Elevation of diaphragm as pregnancy progresses
o Uterine enlargement can elevate the diaphragm up to 4 cm
 reduces reserve volume by 25%
o Rib cage flairs outwards – reducing filling effectiveness
o The work of breathing is increased at rest and during exercise
 Due to diaphragm resistance

Question 9

What are the aerobic changes during pregnancy?

Answer 9

o ↑ Performance in endurance athletic activities
 may improve during the first 12 to 15 weeks of pregnancy, before the increase in body weight and uterine size reduces or stops involvement in competitive athletics.
 The increase in performance results from the increased blood volume and red blood cell mass
o After 2nd trimester PVO2 (mL.kg-1) may ↓
 ↑ oxygen demand of foetus
 ↑ body mass
o Resting oxygen consumption is also increased by up to 15 - 30%
 due to the enlarging uterus and growing foetus
 Increased work of breathing
 when uterine contents are subtracted maternal increases by approximately 4 %

Question 10

What substrates are used during pregnancy?

Answer 10

o ↑ CHO usage
 Foetal demand for glucose is large (main food source)
o ↑ maternal insulin production
 ↑ oestrogen causes β-cell hyperplasia in pancreas
 ↑ Insulin production ⇒ hyperinsulinemia
 Stimulates lipogenesis by the mother increasing fat deposition
o Insulin resistance
 Late gestation, insulin resistance may develop
 2-3% of women have gestational diabetes
• Increased Human Placental Lactogen counters insulin effects
o Reduced CHO use by mother, but this leaves more CHO for foetus
o Mum has to rely more on her body fat → Lipolysis → reduced adiposity

Question 11

What are the gastrointestinal changes during pregnancy?

Answer 11

Increased plasma progesterone (a smooth muscle relaxant) + increased uterine size =
 constipation
 slowing of gastrointestinal motility
 relaxation of the lower oesophageal sphincter, which leads to increased gastric reflux ie: heartburn

Question 12

What are the musculoskeletal changes during pregnancy?

Answer 12

o 60% women experience low back pain during pregnancy
o Anterior displacement of the enlarging uterus
 changes the woman’s centre of gravity
 exaggerates normal lumbar lordosis
o ↑ in hormone levels (especially progesterone, but also relaxing)
 promotes ligament and joint laxity
 Pelvic area susceptible
o The enlarging breasts
 centre of gravity moves inferiorly and anteriorly
 increased weight can contribute to upper back and shoulder pain

Question 13

What are the body massage chances during pregnancy?

Answer 13

Average weight gain ≅ 12 kg 
	fetus 3.5kg 
	Uterus 1.0 kg 
	Placenta 0.6kg 
	Amniotic fluid 0.8kg 
	Breast enlargement 1.5kg 
	Maternal fluid gain 2.0kg 
	Maternal fat 2.5kg