Should a woman exercise during her pregnancy? Yes, if she follows certain guidelines. Guidelines for a prenatal exercise program should take into consideration the woman's initial fitness level and the physiological changes taking place in her body.

Making exercise part of a daily or weekly routine is valuable not only for the duration of pregnancy, but also in preparation for labour and delivery by increasing strength, flexibility, endurance and stamina. Many woman who exercise regularly before they become pregnant find they are able to stick with exercise routines with little or no discomfort.

Studies show active women who continued to exercise throughout pregnancy gained slightly less weight and had 16% fewer Caesarean sections. James Clapp, M.D., professor of reproductive biology at Case Western Reserve in Cleveland, Ohio, conducted several studies with pregnant women. His findings showed fit women had fewer complications such as meconium in the amniotic fluid, abnormal drop in foetal heart rate or core entanglement. Animal studies suggest specific effects of uterine blood flow on a foetus. Due to ethical limits, there is a lack of conclusive research in humans. Thus, exercise standards for pregnant women have been defined conservatively.

The ideal prenatal exercise program offers variety, such as walking, swimming, modified aerobic dance and callisthenics, stretching, cycling, prenatal yoga, etc. Personal preferences help keep women motivated to continue exercise throughout pregnancy.

Physical activity during pregnancy must be approached with particular caution during the first trimester. Some evidence suggests sustained elevation in the mother's body temperature during this time is associated with a greater incidence of defects in the baby's central nervous system. The development of the nervous system, brain and spinal cord begins during the earliest part of the first trimester when many women do not even know they're pregnant. Because of the lack of conclusive research, women are advised to avoid elevated body temperatures during the first trimester and sustain a conservative approach to exercise throughout pregnancy.

Since the first trimester is when hormones cause physiological changes in the woman's body, fatigue and nausea can limit physical activities. By the fourth month, risk of miscarriage is lower and energy level usually returns. This is often the time to begin a prenatal exercise program.

Factors and Fluctuations during Pregnancy
During pregnancy there is a continuous fluctuation of hormones in the body. The influence of these hormones, particularly relaxin, estrogen, progesterone and elastin, begin to soften connective tissue creating laxity in the ligaments and joint instability. This makes the joints more susceptible to injury during exercise.

The woman's centre of gravity changes as breast size increase and the uterus expands to accommodate the growing foetus. Increased spine curvature also causes added strain on the back, particularly in the third trimester.

Sustaining vigorous exercise over 15 minutes many compromise blood flow to the uterus, placenta and foetus due to increased flow to other working muscles and the skin. During normal pregnancy, blood volume increases 30 to 50% to protect against decreased blood flow to the baby. However, target heart rates should be kept 25 to 30% lower than usual or approximately 140 bpm for no more than 15 minutes.

Since the foetus has no means of dissipating heat, hyperthermia is also of special concern. Strenuous exercise for 15 minutes should not increase the body core temperature significantly enough to harm the growing foetus. But pregnant women should maintain adequate hydration at all times.

Components of Prenatal Exercise
Strength, flexibility and cardiovascular fitness are all equally important to a prenatal program. Targeting areas such as upper body and abdominals will help improve posture as the woman begins to experience significant weight gain. Cardiovascular exercise in the form of gentle, low-impact aerobics helps increase endurance and build stamina, which will assist her during labour. Pelvic floors exercises, also known as Kegels, help strengthen the muscles, which surround and support the pelvic organs. These muscles become lax due to hormonal changes in the body. Pelvic tilt movements help alleviate stress on the lower back and strengthen abdominals. Stretch and limbering exercises are important in preparing the muscles and connective tissue and protecting the joints from strain. Relaxation and breathing are important for the woman to release stress and tension from her body and focus on herself and the baby within.

Class Format
Begin seated or standing for a 10-to 12-minute warm-up. Include rhythmic stretches for the upper and lower body using a slow, steady pace. Since pregnancy hormones make joints less stable, it is important to spend ample time warming up. Floor stretches are a good time to introduce the pelvic tilt. In an all-fours position, the pelvic tilt is an effective stretch for the low back. The pressure of the baby is off the back and out of the pelvis. Women will get some relief from backache and tired legs, cramps, pelvic pressure and circulation congestion. Also include side-bending stretches in an all-fours position, known as "tail-wagging," where the hips go from side to side. Pelvic tilts may be done in standing position and could be included before or after aerobics.

Pelvic-Floor Strengthening
Warm-up should also include Kegels. The pelvic floor is a sheet of muscles located at the base of the pelvic, which supports pelvic organs. As the uterus enlarges, there is added stress on the pelvic floor muscles. These under-utilised muscles should be conditioned and prepared for the trauma of childbirth. During a vaginal delivery, the baby passes through the pelvic floor, greatly stretching the entire supporting sheet of muscles. Conditioning the pelvic floor, or perineum, during pregnancy allows more stretch during delivery without tearing and in some cases decreases the need for episiotomy (incision of the vulva to allow sufficient clearance for birth).

Pelvic floor strengthening should resume as soon as possible the postpartum period. Keeping the pelvic floor conditioned will help prevent sagging, urinary incontinence and displacement of the pelvic organs. Kegel exercises may be done seated, standing, on all fours or elbows and knees depending on what is comfortable for the woman. If Kegels are not done during the warm-up, they may be done as a standing exercise or during relaxation.

Aerobics
The 15- to 30-minute segment should consist of gentle, low- to moderate-intensity, low-impact aerobics. The pace should be slow enough to keep participants' heart rates under 140 bpm. Remember the extra weight will cause a woman to move slower and get tired more quickly. Exercises should have simple choreography without a lot of abrupt changes in direction.

The way different pregnant women will respond to the same exercise varies, therefore limit strenuous exercise to 15 minutes. Remember to bring the heart rate down gradually in the last five minutes and follow the aerobics section with gentle stationary stretching, either standing or on the floor. After the aerobics section, take a heart rate to be sure you not working above 140 bpm.

Stretch
Unlike traditional aerobics, prenatal exercise stretching is often recommended throughout the class. After aerobics and prior to strengthening work, spend a few minutes stretching the muscles. If you plan work in a standing position, stretch in a standing position or at a bar. This makes smoother transition.

Upper Body
Strengthening the upper back, chest and shoulders is particularly important for posture, balance and preparing you for for lifting and carrying your newborn. The best positions to work the upper body are standing or seated. In standing position, utilise a ballet bar or wall to do push-ups. The use of restrictive bands in an effective way to condition the upper body either standing or seated.

Lower Body
Strengthening exercises should include quadriceps, gluteus, hamstrings, inner and outer thighs, plus strengthening of calves and ankles. Lower body muscle strength is important for general balance and tone. Ankle rotations help the veins return blood from the lower legs and minimise varicosities and swelling of the ankles. Calf strengthening can prevent leg cramps, which are common in pregnancy. Leg cramps can be brought on simply by pointing the foot. Therefore, when performing calf-strengthening exercises, flex and relax the foot rather than flex and point.

Lower body strengthening can be done standing with squats, plies, lunges and leg lifts to the front, side or behind the body. A ballet barre, table or chair back provides extra support. In a seated position, bands provide effective muscle resistance work while side-lying positions offer the support necessary for working against gravity.

Abdominals
As the uterus continues to grow, the abdominal muscles are stretched and weakened. If they become too weak they will not be able to assist during labour. As the woman gains weight, her centre of gravity also moves forward, increasing stress on the lower back. The pelvis is forced to tip forward which affects posture. The results are often fatigue and backache. Exercising the abdominals throughout pregnancy helps alleviate some of the back stress and maintain the elastic qualities of the muscle to better support the pelvis, pelvic organs and the growing baby.

ACOG guidelines indicate after the fourth month, when the enlarged uterus puts pressure on major blood vessels in a supine position, traditional sit-ups should be avoided. If a woman chooses to continue sit-ups after her fourth month, she must not maintain that position for more than three minutes at a time, and she should stop if she experiences dizziness. Modify sit-ups by simply changing to a side-lying or C-curve position. In these positions there is no longer pressure on the blood vessels.

Pelvic tilting for the purpose of abdominal strengthening can be done seated or standing in addition to the all-fours position. As pregnancy advances, the pelvic tilt must be controlled against the increasing weight of the pelvic contents. Pelvic tilting on hands and knees or all fours position is the most effective way to work the muscles against gravity. Proper breathing enhances the benefit of this exercise. Inhalation should take place when the baby moves closer to the floor expanding the abdominals, and exhalation when the abdominals are lifted and contracted.

Strength and Relaxation
Effective relaxation is essential for good health. "Genuine relaxation requires insight into our muscular system with which we make all purposeful actions in life and express our emotions," says Elizabeth Noble, author of Essential Exercises for the Childbearing Year. Relaxation is the time to release stress from the body during the state of restful alterness. This can be done with imagery, music, and silence, breathing techniques and inward focusing. Deep breathing aids blood circulation and helps the mother to balance psychologically and physiologically. It is important to include these few minutes to release the body and mind from tensions. Stretching may be incorporated before, during or after the relaxation phase. Perform relaxation lying on the side, seated or on all fours. Lying on the left side of the body is a safe and comfortable position.

All the major muscle groups should be stretched at the end of class. Include reaches for the upper body, straddle stretches for the back, inner thighs and hamstrings, shoulder rolls and partial head circles, cat stretches for the back and torso rotations for oblique and outer thighs. Squatting provides effective positions for good body mechanics. In a pregnancy squats, the feet are flat and wide apart, hips drop below the knees and the centre of gravity is lowered. The pelvis is tilted backward and the spine is held straight. As the elbows rest on the knees for balance, calf muscles get a good stretch. Squatting is a wonderful position for labour since the pelvis is at its widest. The force of the abdominals and gravity also help the baby down the birth canal. Practising this position helps prepare the body before labour.

Guidelines and Limitations

• Avoid deep flexion or extension of the joints. Stay within the joints' range of motion.
• Avoid activities with a lot of rapid, repetitive jumping or jarring movements and sudden directional changes.
• Limit vigorous exercise to 15 minutes.
• Keep heart rate below 140 bpm.
• Precede vigorous exercise with a low-intensity warm-up, which includes rhythmic stretching.
• Finish with a gradual decrease of intensity, which includes static stretching.
• Stop physical activity if any unusual symptoms appear and contact your doctor.
• Avoid exercises in the supine position (back lying) after the fourth month. If you don't feel any dizziness, you may exercise in supine position for up to three minutes.
• Drink plenty of fluids before, during and after exercise.
• Get a doctor's approval to exercise.