You're pregnant! Congratulations! Your body's changing-wondrously, marvelously. One unexpected and unwelcome change may be lower back pain. As unwelcome as it is, lower back pain is a logical consequence of pregnancy. Let's look at the major cause of pregnancy-related lower back pain.

After possible medical causes have been investigated and eliminated, pregnancy-related lower back pain can be categorized as mechanical in nature. The weight of your growing baby, plus the weight of the placenta and amniotic fluid, create an unbalanced mechanical load in front of your lower back. Spinal joints are brought closer together as a result of these mechanical stresses, irritating the ligaments that hold the vertebras together and the muscles that move the vertebras. Such irritation may result in lower back pain or even muscle spasm and painful, restricted motion.

Not all pregnant women develop lower back pain, but many do. Lack of physical conditioning can lead to lower back pain even when you're not pregnant, and conditioning is certainly a factor in pregnancy-related lower back pain. Stress is also a factor. Stress, very often, is the key factor at any time in cases of mechanical lower back pain. The unbalanced load of pregnancy makes the lower back more susceptible to stress-related injury.

The best method of preventing back pain in the first place is being fit. And, the good news about fitness is that it's never too late to start. Aerobic exercise, nutritional common sense, abdominal exercise, and light weight—lifting make up a sound fitness program. Of course, obtain the advice and approval of your obstetrician first, if you're considering starting a new exercise program after you've become pregnant.

Always be sure to stretch before each exercise session. Stretching in the morning is a good idea, anyway, even on days when you're not exercising. Stretch the back of your thighs (hamstrings), your calves, and the front of your thighs (the quadriceps). Stretching these leg muscles helps the lower back to function effectively. Stretch gently and slowly--no bouncing. [See NB News articles "Stretches for Joggers, Runners and Walkers" for a leg stretching program and "Back Pain Causes and Treatments" for some back stetches.]

Stretching, aerobics, light weight-lifting, abdominal exercise, and nutritional common sense are elements of a fitness program that anybody can follow. The result, over time, is a healthy body and, by implication, a healthy lower back.

If you are experiencing lower back pain, consult with your obstetrician—make sure it's only a mechanical problem and not a medical condition. The severity of pain is not an indicator here—mild mechanical problems, easily treated, can often be associated with severe, debilitating pain.

There are a few subtle things you can do to help yourself. You are different when you are pregnant, and it's useful to acknowledge the difference. It may be appropriate to rest more, and to reduce your usual level of activity. Let someone else carry the heavy packages. Let someone hold the door open for you. Sleep a little more. We're often reminded to "listen to your body." The advent of pregnancy is a good time to start doing this, to pay more attention to yourself as a physical person, rather than as a mind or personality who is carrying a body around from place to place.

Ultimately, stuff happens, and even though you are fit, you may still experience lower back pain at some point during your pregnancy. Women are often concerned that once lower back pain starts, they will have it for the duration of the pregnancy. However, with appropriate treatment and rehabilitation (stretching, gentle exercise), most cases of pregnancy-related lower back pain resolve satisfactorily.

Dr. David Lemberg, the author of Commitment to Fitness: Real Fitness for Real People, is a board-certified chiropractic orthopedist in his twentieth year of private practice on Manhattan's Upper East Side. He has been published in national trade magazines such as Muscle & Fitness and Dancemagazine, the peer-reviewed Topics in Clinical Chiropractic, the Florida Chiropractic Society Review, and The Chiropractic Journal. Dr. Lemberg is a member of the postgraduate faculty of Los Angeles College of Chiropractic, and for the last ten years has taught orthopedics to chiropractors in venues across the United States and in Canada. He was Clinical Editor of the quarterly journal, Spinal Manipulation, published by the Foundation for Chiropractic Education and Research, from 1990 through 1995.

Commitment to Fitness: Real Fitness for Real People may be ordered through Dr. Lemberg's web site. His office is accepting new patients: 212-535-7429.