Studies have been carried out all over the world to help doctors decide which asthma medicines are safest in pregnancy. The single biggest risk to an asthmatic woman’s pregnancy is poor asthma control in the mother. Uncontrolled asthma is very harmful to the developing baby and can result in devastating complications for both mother and child.
Complications of poorly controlled asthma include pregnancy-induced hypertension, preeclampsia and eclampsia in the mother, preterm labor and premature birth, intrauterine growth retardation, and low-birth-weight babies, along with increased perinatal morbidity and mortality. Inadequate control of the mother’s asthma leads to a reduced oxygen supply to the developing baby (maternal hypoxia), as well as a decreased blood supply to the womb. All pulmonary specialists agree that they should treat their pregnant asthma patients with asthma medicines that are not only highly effective, but also as safe as possible for both mother and baby.
The FDA classifies all medicines approved since 1980 into one of five different categories. The FDA classification is based on studies of safety in pregnancy. The five categories are A, B, C, D, and X (Table 56). Category A is considered the very safest, while Category X drugs are absolutely contraindicated in pregnancy under any circumstances. No medications are labeled Category A for use in pregnancy, because the A designation would indicate that relevant drug studies were performed in pregnant women and no such studies have ever been carried out.
The safest medicines for practical purposes are labeled as Category B, based on anecdotal reporting involving long-term use in pregnant women and exten-sive studies (involving pregnant laboratory animals) that produced no evidence of harmful side effects. A Category C designation indicates that the drug has been responsible for some adverse effect on the fetus in animal studies.
Drugs in the C category may perhaps carry an increased potential developmental risk to the human fetus, but they are still considered safe for use in pregnant women in part because the dose of medicine used in these animal studies is far, far greater than would ever be given to a human. The decision to use a medication in Category C is deter-mined on a case-by-case basis, most often when the clinical situation is such that the potential risk of not using a Category C medication is greater than the possible risk associated with taking the drug.
There are no asthma medicines classified as Category A, as mentioned previously. Most medicines used in asthma treatment fall into Category C, and several are classified in Category B. All quick-relief, short-acting β2 agonist inhaled bronchodilator medications (SABA) are classified as Category C, even though they have been in use for over 2 decades and are widely viewed as very safe by the medical profession. All long-acting β2 agonist inhaled bronchodilators (LABA) are also Category C medicines.
The inhaled β2 agonist medicines have not been shown to have adverse effects on the course of the pregnancy, and have not been shown to be harmful to the human fetus. The C classification for the β2 agonist group of inhalers reflects the absence of studies in pregnant women. One inhaled corticosteroid preparation, Pulmicort (budesonide), is in Category B; all other inhaled steroids are, as of this writing, labeled Category C. The daily use, long-term inhaled controller medicines Intal (cromolyn) and Tilade (nedocromil) are in Category B, as are the leukotriene modifier tablets Singulair (mon-telukast sodium) and Acolate (zafirlukast). The new IgE blocker Xolair (omalizumab) carries a Category B rating.
The theophylline medicines are all Category C drugs.Because both uncontrolled asthma and poorly controlled asthma in the mother have such serious consequences for her and for her unborn child, the guiding principle in the treatment of asthma in pregnancy is to achieve opti-mal asthma control even if daily medication is required.
It is crucial to normalize maternal lung function and ensure that the mother is not experiencing any symptoms of asthma. Pulmonologists take the point of view that any medicine that is required for best asthma treatment should be administered to a pregnant woman. For example, steroid bursts for treatment of an exacerbation are used in the setting of pregnancy just as they are when a woman is not pregnant.
As a rule of thumb, we would use Category B medicines first, adding any required medicines that may fall into the C category (or even D), if needed to achieve good asthma control. If you are pregnant and have any questions or any concerns about the safety of the medicines you have been prescribed, you should consult with your treating physicians.
Both your obstetrician and your asthma doctor have the expertise to counsel you and give advice that is best for you. Under no circumstances should you stop your prescribed asthma regimen or not follow the treatment plans recommended by your doctor.