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Practical Parenting
Exercise and Pregnancy: What Does Research Say & Busting the Myths

While older generations have been of the opinion that exercise could possibly be bad for pregnant women and their babies- the opinion held by active women has been to the contrary. The conflict between these two opinions was the basis of the pregnancy research that has been done over the last 30 years by James F Clapp MD. His research has not only nullified the myths surrounding exercise while pregnant, but has provided amazing results in women who choose to remain exercising through this time.

One of the most confusing areas has been using heart rate as an indicator of whether a women is exercising at the right intensity. Heart rate is dependant on many factors- for example genetic make up (this can vary heart rate by 15-30 beats per minute),Age (a 20 year old will have a heart rate higher than a 30 year old), prior level of fitness (a fit person will have a lower heart rate than someone who does not exercise ),variation of heart rate throughout the day as well as with different types of exercise and, finally, heart rate depends on hydration- when a women is adequately hydrated her heart rate will be slower. What stage of pregnany a women is at will also vary the heart rate. In early pregnancy when blood vessels are relaxed and dilated but there is not yet adequate volumes of blood, heart rate will increase. In late pregnancy when there is more fluid and blood a women’s heart rate will be lower. This means the same women exercising in early pregnancy will have a higher heart rate than when she does the same exercise in her first trimester.

Therefore unless heart rate is constantly monitored at all times of the day and doing all activities it becomes and unsafe, unreliable measure on which to base exercise intensity for the individual. Rather a perceived scale of exertion- known as the Borg scale becomes a far more reliable indicator.
 

6	no exertion
7
8	extremely light
9	very light
10
11	light
12
13	somewhat hard
14
15	hard
16
17	very hard
18
19	extremely hard
20	maximum exertion

This scale works on the logical principle that how a women feels is the best indicator of how hard she is working. It is still common for professionals and books to recommend that a woman not exercise over 140bpm, however this figure was removed from obstetric guidelines in 1994 but is still a myth perpetuated by old wives tales!

Beginning in early pregnancy the increase in the hormone progesterone stimulates breathing which improves the movement of gases to and from the baby. Women feel short of breath but their lung function remains normal. Trained individuals need to breather less air to get the same amount of oxygen as non-exercisers.

Exercise not only improves the body's ability to transport oxygen to the muscle cells but also the cell's ability to use the oxygen for work. Exercise also increases the number of metabolising units in the body. These factors mean improved muscle strength and endurance.

From the baby's side – the placentas of women who were exercising regularly in early to mid pregnancy grow faster and function better than those of health women who do not exercise. Secondly both pregnancy and exercise increases blood flow so the effect is cumulative. What this means is that during exercise the mother maintains a higher blood flow to the baby. This is also true of unanticipated events such as dehydration or haemorrhage.

Another common tale is women should not overheat when pregnant. While this sounds correct the truth is that pregnant women who exercise can generate 20% more heat without raising their body temp because they have 20% more tissue to keep warm. Research on pregnant women has shown that pregnancy reduces the risk of a mother’s temperature rising high enough to bother her baby by improving her ability to lose heat through her lungs and skin. Pregnancy also results in sweating to begin earlier, further reducing body temperature. Once again exercise adds to this by improving the ability to rid the body of heat by dilating blood vessels and causing sweating at a lower body temperature. Therefore A WOMAN WHO EXERCISES WHEN PREGNANT CAN DEAL MORE EFFECTIVELY WITH HEAT STRESS THAN A WOMAN WHO DOES NOT EXERCISE.

Exercise IN PREGNANCY ALSO ENHANCES ALMOST ALL MUSCULOSKELTALFUNCTION.

Another concern about women is that exercise during a normal pregnancy can increase the risk of miscarriage and premature birth. All the research done on vigorous exercisers has shown that in a normal pregnancy vigorous exercise (running etc) does not increase the risk of miscarriage, premature birth, membrane rupture or congenital defects.

A lot of hype in the media recently has made claims that women who exercise have smaller babies. It is important to clarify that women who exercise have leaner babies with less body fat. The researcher asks the question 'is a bigger baby better if it only has more fat?' In addition babies born of women who exercise do not differ in their organ size or bone lengths. Follow up studies of the babies of women who exercised at 1 and five years of age showed at one year of age exercisers' babies did better on standardised intelligence tests than children of mothers who did not exercise. Their mental and physical performance was better as well. At age five children of exercisers were less fat and scored much higher on tests of general intelligence and oral language skills than the children born to non-exercisers.

It is true that the baby's heart rate rises when the mother is exercising. Research done to see whether this meant the baby was in distress has shown this is not the case. During labour the babies born to exercisers have less lack of oxygen than the non exercisers and these babies tolerated contractions better than the non exercise group. It has also been found that in exercising mothers the incidence of cord entanglement and meconium staining fetal distress) is significantly reduced in women who exercised when pregnant. Once born the exercising babies tend to be more alert and easier to care for.

The benefits for the mother are multiple. It is firstly worthwhile to note that a woman who exercises and ceases to exercise prior to 30 weeks pregnant will lose all the benefits she gained while exercising and is no better off than her non exercising counterparts.

Research has shown that during labour women who exercise have a 35% in the need for pain relief, 75% decrease in the incidence of maternal exhaustion, 50 percent decrease in the need to artificially break waters, are 50% less likely to be induced or need intervention in labour (fewer cases of fetal heart abnormalities,) 55% decrease in the need for episiotomy and 75% decrease in the need for forceps and caesarean sections.

Regular exercise has been seen to shorten labour by a third. Other benefits include limiting fat deposition and reducing weight gain in pregnancy. Maternal discomforts such as back pain and pelvic pain are reduced. Women who exercise get ill less due to a better immune system. There is an increase in maternal fitness and sense of well being and a good body image.

Simply put exercising during pregnancy is safe and effective and carries with it incredible benefits to both mother and baby.

It is also interesting to see that the research has been done on women who ran, did cross country skiing or step classes. Once again all of these are activities that are traditionally cited as 'no- no’s' in pregnancy. Interestingly the above benefits were not seen in women who simply walked as an 'exercise activity'!

While we recommend that all women exercise when pregnant it is vital to discuss your exercise options/plans with a doctor or specialist in the exercise and pregnancy field. You will need to be screened to ensure there is nothing about you or your pregnancy that may contraindicate (preclude you from )exercise. Once cleared begin slowly, gradually increasing your intensity as long as you are comfortable (12-15 on the Borg scale). Report any changes or concerns to the person caring for you. Always include cardiovascular as well as weight bearing exercise in your regime to gain maximal benefits.

Above all enjoy this phase in your life- it truly is a special time.
(please see below for a list of do’s and don’ts):
 

1.	Avoid hot humid environments with poor ventilation
2.	Drink frequently to stay well hydrated
3.	Eat regularly
4.	Don’t ignore persistent pain or bleeding
5.	Don’t exercise to the point of exhaustion