Sunday, March 13, 2011

Benefits of Exercising During Pregnancy

I.  Introduction
II.  Gestational Diabetes Mellitus
III. Pre-eclampsia
IV. Pre-term Delivery, Birth Weight, and other Benefits
V.  Author's recommendations
VI. Bibliography
 I.  Introduction

If you didn’t know by now, unhealthy eating habits put us at risk for developing many disorders such as cardiovascular disease and cancer.  However, pregnant women who live unhealthy lifestyles also put their unborn child at a much greater risk for health complications.  Aside from abundant health issues associated with unhealthy eating, women with a high pre-pregnancy BMI or women who consume large amounts of saturated fat and simple carbohydrates are at risk for developing gestational diabetes mellitus or pre-eclampsia.  Newborns are also at a greater risk for abnormal birth weight, pre-term delivery, obesity or type 2 diabetes later in life.

As some may assume, proper dieting and exercise is often prescribed to at risk pregnant women to prevent the development of these ailments.  I won’t focus on the dieting, because I don’t think that the benefits of healthy eating during pregnancy can be disputed.  Many health ailments can be avoided by following the eating habits that I outlined in ‘Healthy Eating 101’.  However, some women may not want to exercise during pregnancy in fear of its effect on their unborn child.  Well, the fact is, a sedentary life is more likely to negatively effect your child’s development than an active life.  Hopefully this column will change some of those minds.

Many researchers have investigated the benefits of recreational exercise or leisure time physical activity (LTPA) during pregnancy.  Common types of this exercise include brisk walking, bicycling, canoeing/rowing for pleasure, dancing, exercising on a treadmill or elliptical, gardening, playing golf, playing tennis, aerobics, jogging, or swimming (just to name a few).  Some of the studies that will be discussed do not specify one type of recreational exercise, so keep this list in mind.  

II.  Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is a form of hyperglycemia in which insulin supply is not adequate to meet the body’s demands for blood glucose regulation.  In a normal pregnancy, the ability of insulin to clear glucose from the blood progressively decreases beginning near mid-pregnancy, developing an insulin resistance similar to that of type 2 diabetes.  To counteract this, pancreatic β cells increase their insulin secretion to compensate for this insulin resistance in pregnancy [1].  However, most women who develop GDM have already developed a chronic insulin resistance [1], which can develop from a diet high in carbohydrates that are high on the glycemic index [2] and results in decreased pancreatic β cell function [1].  This disorder puts women at high risk for developing diabetes following pregnancy [1].  It may also lead to pre-term delivery, which dramatically increases infant mortality.   As you might expect, insulin sensitivity can be increased with low GI, high-fiber diets with more protein and vegetable consumption [3, 4], thus lowering the risk of GDM.  However, exercise is also an effective way to lower GDM risk.

Various studies by Dempsey et al. have demonstrated the ability of exercise before and during pregnancy to reduce the risk of obtaining GDM.  Results from these studies show that women who participated in recreational exercise during the first 20 weeks of pregnancy had a 48% reduction in risk of GDM when compared to inactive women [5].  Women who took part in recreational exercise for ≥ 4.2 hours per week the year before pregnancy also demonstrated a 76% decrease in GDM risk [6].  Lastly, women who exercised both before and during pregnancy experienced a 69% GDM risk reduction [6].
III.  Pre-eclampsia

Pre-eclampsia is a dangerous pregnancy complication that affects as many as 10% of pregnancies per year.  Symptoms include high blood pressure and excessive protein in urine that may develop from 20 weeks gestation.  While the exact mechanism is unknown, some theories suggest that diet, endothelial dysfunction, insulin resistance, coagulation activation, and increased inflammatory response may play a role [7]. Pre-eclampsia also increases the risk of pre-term delivery.

As is the case with GDM, physical activity can also reduce the risk of developing pre-eclampsia. 

A study by Sorensen et al. has shown that [8]:
1.  Women who participated in recreational exercise during early pregnancy had a 35% reduction in risk of pre-eclampsia when compared to inactive women.
2.  Women who participated in recreational exercise one year prior to pregnancy had a similar reduction in pre-eclampsia risk.
3.  More specifically, women who exercised for 3.8-6.7 hours per week during the first 20 weeks of pregnancy had a 68% reduction in risk of pre-eclampsia.
IV.  Pre-term Delivery, Birth Weight, and other Benefits

One important predictors of the survival and health of a newborn is the time of delivery.  A normal pregnancy typically should last about 40 weeks.  Pre-term delivery occurs when a pregnancy ends between 20 and 37 weeks.  When this occurs, the newborn is much more at risk to many health problems, neonatal mortality, and neonatal morbidity [7].  Birth weight is also a great predictor of newborn health.  Infants with birth weights of < 2,500 g have increased risk of mortality, morbidity, adulthood hypertension, and diabetes [7].  Infants born at birth weights of > 4,000 g have also been shown to increase the risk of adulthood type 2 diabetes and breast cancer (in females) [7]. 

Fortunately, recreational exercise can reduce the risk of both pre-term delivery and unhealthy birth weights.  Pregnant women who participated in recreational exercise demonstrated a 50% reduction in risk for pre-term delivery [9].  Studies also showed that aerobics, jogging, swimming, moderate-fast biking) during the first or second trimester does not increase the risk of pre-term delivery [10].  Also, the reduction in GDM risk from exercise suggests that exercise reduces GDM-induced pre-term deliveries.

Recreational exercise also reduces the risk of unhealthy birth weights.  A study conducted by Clapp et al. placed sedentary, pregnant women on an exercise program for 20 min, 3-5 times per week, beginning at 8 weeks and continuing through the duration of the pregnancy.  The exercise program consisted of treadmill exercise, step aerobics, or a star stepper at a low intensity (55-60% pre-conception VO2 max).  Women in the exercise group gave birth to babies with significantly more lean body mass, length, and weight.  Placental growth rate and function were also greater in the exercise group [11]. 

Other benefits of exercise during pregnancy [12]:
-Maintenance of vascular reactivity and blood volume, which can decrease in sedentary pregnant women, leading to hypotension (low blood pressure) or arrhythmias (irregular heart rate).  Women who exercise prior to pregnancy and maintain it during pregnancy are protected the most.
-Vascular remodeling within the uterus is heightened; increases placental size and uteral blood flow.
-Glucose utilization is increased while lowering insulin secretion (lowers risk of GDM)
-Women gain less weight, maintain posture, and maintain abdominal muscle tone following child birth.
-Babies have decreased fetal distress before or during labor, decreased growth of fat, and normal to superior cognitive development.
V.  Author's Recommendations

1.  If you are currently sedentary but plan to conceive a child within the near future, begin a regular exercise routine to lower the risk of GDM, pre-eclampsia, and improve the development of your child.
2.  During pregnancy, continue to exercise 3 or more times per week for 30-60 min (see the list of exercise routines in the introduction)
3.  Keep your doctor informed about your exercise regimen in order to monitor your health and the healthy development of your child.

The key to ending many diseases that kill us is to stop facilitating the reproduction of children genetically pre-disposed to developing these diseases.  And it starts with the parents…even before conception...

Dr. O 
"I don't live to eat...I eat to live!"
VI.  Bibliography

1.       Buchanan, T.A. and A.H. Xiang, Gestational diabetes mellitus. Clinical Investigation, 2005. 115(3): p. 485-491.
2.       McKeown, N.M., et al., Carbohydrate Nutrition, Insulin Resistance, and the Prevalence of the Metabolic Syndrome in the Framingham Offspring Cohort. Diabetes Care, 2004. 27(2): p. 538-546.
3.       Boden, G., et al., Effect of a Low-Carboydrate Diet on Appetite, Blood Glucose Levels, and Insulin Resistance in Obese Patients with Type 2 Diabetes. Ann Intern Med, 2005. 142(6).
4.       Fukagawa, N.K., et al., High-carbohydrate, high-fiber diets increase peripheral insulin sensitivity in healthy young and old adults. Am J Clin Nutr, 1990. 52: p. 524-528.
5.       Dempsey, J.C., et al., A case-control study of maternal recreational physical activity and risk of gestational diabetes mellitus. Diabetes Res Clin Prac, 2004. 66(2): p. 203-215.
6.       Dempsey, J.C., et al., Prospective Study of Gestational Diabetes Mellitus Risk in Relation to Maternal Recreational Physical Activity before and during Pregnancy. Amer J Epidem, 2004. 159(7): p. 663-670.
7.       Hegaard, H.K., et al., Leisure time physical activity during pregnancy and impact on gestational diabetes mellitus, pre-eclampsia, preterm delivery and birth weight: a review. Acta Obste Gyn, 2007. 86: p. 1290-1296.
8.       Sorensen, T.K., et al., Recreational Physical Activity During Pregnancy and Risk of Preeclampsia. Hypertension, 2003. 41: p. 1273-1280.
9.       Berkowitz, G.S., et al., Physical activity and the risk of spontaneous preterm delivery. Reprod Med, 1983. 28: p. 581-588.
10.     Evenson, K.R., et al., Vigorous leisure activity and pregnancy outcome. Epidemiology, 2002. 13: p. 653-659.
11.     Clapp, J.F., et al., Beginning regular exercise in early pregnancy: Effect on fetoplacental growth. Amer J Obstet Gyn, 2000. 183(6): p. 1484-1488.
12.     Clapp, J.F., Exercise during Pregnancy: Risk and Benefits, in Protocols for High-Risk Pregnancies: An Evidence-Based Approach, ed. J.T. Queenan, J.C. Hobbins, and C.Y. Spong. 2010, Oxford, UK: Wiley-Blackwell.


Muhammad said...

What an amazing content is this and surely it makes realize each and everyone who read this.Found your communication dynamics very valuable.
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Michelle said...

I really enjoyed this article! I can say that my experience has been that all of the above is true! I'm enjoying a pretty low-key pregnancy and I do owe some of that to making good exercise choices. In general, I think doctors/the public are becoming more accepting of seeing a pregnant lady out for exercise like a run (albeit I've gotten a few strange looks and comments). My daughter will have a half marathon, 10k race, 5k race, and probably a few more runs under her belt before she's even born! I hope this sets the stage for both her and my son to love sports and activity as much as I do.

Supplements Canada said...

Mild exercises are important in pregnancy. Pregnant women should always be healthy and these exercises can help them maintain their health.

Fitness Food And Style said...

This is so true! I was able to exercise throughout my last pregnancy (lucky last baby no.4) and I found it to be so much more invigorating, more energy throughout the day with my other 3 children and what an easier journey it was to get back to my pre baby body. Great post! XxDani

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