Pregnancy is an exciting time in a woman's life, and a time when health concerns are paramount. If you are pregnant, you want to do what's best for your baby. In general, the message to a pregnant woman is avoid taking medications whenever possible to limit the potential for developmental problems in the growing fetus.

But, if you are a woman with asthma who is pregnant, you should realize that keeping your asthma under control, with medications when necessary, is best for your baby.

What we know from studies is that when asthma is well controlled, you are less likely to have complications during your pregnancy. The biggest danger for the fetus in women with asthma is undertreatment. Blood oxygen levels are likely to be below normal in a woman with poorly controlled asthmas, and the same would be true for the baby she is carrying. If the low oxygen levels are serious and prolonged enough, it can cause brain damage to the baby.

Other problems associated with poor asthma control in pregnancy include intrauterine growth retardation, low birth weight and even fetal death. For the mother, poor asthma control has been linked to preeclampsia, the development of high blood pressure and other symptoms at the end of pregnancy or during childbirth. Preeclampsia is a serious medical condition that can cause kidney, brain, liver or eye damage in the mother, and seizures in the mother or baby.

Remember that there are many things you can do to prevent asthma flares without medications. If you have not carefully identified your triggers and evaluated your environment before, your pregnancy is the best reason to evaluate your prevention strategies now.

Common allergens that can trigger asthma attacks include dust mites, mold and animal fur. Sometimes asthma is triggered by cold or dry air or exercise. There are measures you can take to reduce the allergens in your environment by cleaning and removing suspected exposures or adding protective covers to your pillows and mattresses.

Exercising in a humidified environment (like a swimming pool) can help. Frequent hand washing is recommended to minimize exposure to viruses that cause colds and flu, which also can trigger asthma attacks. And, of course, if you smoke you should stop and avoid exposure to secondhand smoke.

If you were receiving allergy shots before your pregnancy, you can continue these. If you are already pregnant, it is safer to wait until after you deliver to have to appropriate testing and treatment to avoid a reaction during your pregnancy.

Measuring your peak flows, even when you feel good, is another way to follow the course of your asthma during pregnancy. Often, you can tell if your peak flows are falling before your breathing has changed and make adjustments to your medications early. Conversely, good peak-flow measurements help tell you when to taper back medicines to the lowest dose that makes you feel well, and don't affect your peak flow.

In general, pregnant women with asthma, like other chronic illnesses, are advised to take medications with proven pregnancy safety records whenever possible, sticking to one medication when possible and using the minimum dose for the shortest possible period. If drugs can be avoided during the first trimester, that is the best way to minimize risk to the fetus. When possible, drugs should be given topically (inhaled) rather than systemically (pills).

Based on current information and studies, the general practice and medication preferences include:

• For mild asthma symptoms that occur less than a couple times per week, inhaled beta-agonists (such as albuterol) are recommended to be used only when symptoms occur.
• If asthma symptoms are more frequent, use inhaled cromolyn daily to reduce inflammation in the airways. Animal and human studies suggest that it is safe in pregnancy.
• If asthma symptoms still are not controlled, a low-dose inhaled corticosteroid is recommended for daily use.
• Theophylline may be the next drug added to a regimen if asthma is not well controlled with the above medications. Some doctors prefer to go to the next step rather than use theophylline.
• For more severe asthma, a higher-dose inhaled corticosteroid may be needed.
• For severe asthma or an asthma attack that is not controlled with the above medications, oral corticosteroids (such as prednisone or Medrol) are needed to protect the health of the mother and fetus. The goal is to taper the corticosteroids over a week or two once the symptoms are controlled.

It is difficult to predict what effect pregnancy will have on asthma. About one-third of women with asthma get worse, about one-third get better and one-third stay the same.

If asthma does worsen during pregnancy, the change usually takes place in the second and third trimesters. Also, if your asthma was worsened by a previous pregnancy, it is more likely to flare with future pregnancies.

If your asthma is under control during your pregnancy, it is unlikely to cause any problems during labor and delivery.