Using Medication for Asthma While Pregnant

Asthma is a very common medical condition. In fact, asthma is present in about 3% to 8% of all pregnancies.

Unlike some conditions where you can stop a medication during pregnancy, people with asthma need to take their medication to maintain good control. This leads many people to ask questions about the safety of asthma medications during pregnancy, such as: How will pregnancy impact my asthma control? Will asthma make my pregnancy high-risk? Will it cause harm to the baby or to me?

Pregnant woman holding her belly
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Asthma Control During Pregnancy

Asthma control in pregnancy can be thought of by a rule of thirds—one-third of pregnant people experience improved asthma control, a third show no change, and the final third experience a worsening of their symptoms.

In general, your asthma severity before becoming pregnant is related to your asthma severity during pregnancy.

While one might think that asthma control would worsen as your belly grows, it turns out to be just the opposite, and asthma is less severe in the last weeks of pregnancy. When asthma control improves, it seems to do so gradually over the course of the pregnancy.

In those whose asthma gets worse, the worsening was most common between 29 and 36 weeks of pregnancy. Asthma attacks seem to occur more commonly during the second and third trimesters. Significant asthma symptoms are uncommon during labor and delivery.

Finally, the asthma course during pregnancy tends to repeat itself over subsequent pregnancies. If your asthma improved or worsened during a previous pregnancy, it tends to follow the same course with future pregnancies.

The Impact of Asthma on Pregnancy

Poorly controlled asthma can lead to all of the following complications:

  • Infant death
  • Preterm delivery
  • Low birth weight
  • Miscarriage
  • Bleeding both before and after delivery
  • Depression
  • Preeclampsia or pregnancy-induced hypertension
  • Blood clots or pulmonary embolism
  • Congenital malformations
  • Hyperemesis, a vomiting disorder
  • Complicated labor

These complications may result from decreased oxygen levels. Decreased oxygen levels in the mother can lead to decreased oxygen levels for the baby and decreased blood flow to the placenta. The more severe your asthma, the more likely you are to have asthma complications.

Asthma medications can also lead to complications during pregnancy.

None of the changes related to asthma control or the effect of asthma on pregnancy should be taken to mean that those with asthma should not get pregnant. Good treatment and control will minimize the risk of these complications.

Asthma Treatment in Pregnancy

Your asthma treatment in pregnancy is not all that different than your treatment in the non-pregnant state. You need an asthma action plan, you need to regularly monitor your asthma symptoms, and you must attempt to avoid triggers.

One of the things that makes monitoring a little more difficult in pregnancy is the sensation of shortness of breath many pregnant patients get, especially later in pregnancy. However, coughing and wheezing are never normal symptoms of pregnancy and could be a sign of poor asthma control.

As a result, monitoring asthma with peak flows or FEV1 may be more reliable in pregnant patients. A decrease in either of these may suggest an asthma exacerbation.

As with the non-pregnant patient, quitting smoking is important. Not only does smoking increase the risk of an asthma exacerbation, but it can make low oxygen levels worse and potentially increase the risk of experiencing one of the previously mentioned complications.

Likewise, avoiding other irritants such as dust, dander, and dust mites is an important part of your action plan.

Medications During Pregnancy

Related to asthma treatment in pregnancy, two questions commonly arise related to medications:

  1. Do asthma medications have adverse effects on a developing baby?
  2. Does pregnancy alter a particular medication's effectiveness compared to its effectiveness in the non-pregnant state?

Asthma medications during pregnancy have been associated with a number of serious adverse outcomes, such as:

  • Miscarriage
  • Death
  • Congenital malformations
  • Decreased growth
  • Poor development
  • Decreased blood flow to the placenta
  • Increased risk of preterm delivery

However, one should be aware that all of these adverse effects are common in pregnancy, even in those without asthma. For example, congenital anomalies occur in 3% of live births and miscarriages occur in 10% to 15% of pregnancies.

Most asthma drugs have not been proven safe in controlled trials of pregnant women. Many have not demonstrated any fetal risk in animal studies, but there haven't been controlled studies in people. For other medications, some risks were identified in animal studies that were not subsequently confirmed in human studies in the first trimester of pregnancy, and there is no evidence of risk later in pregnancy.

In general, it is felt that active treatment to maintain good asthma control and prevent exacerbations outweighs the risks of most regularly used medications for the treatment of asthma.

Albuterol, beclomethasone, and budesonide have all been studied in pregnancy, and the outcomes have been reassuring. On the other hand, studies with oral prednisone have not been as reassuring. There are also a number of drugs that have very little human experience in pregnant patients.

SABAs

Short-acting beta-agonists provide quick relief for asthma symptoms such as:

While extremely high doses of SABAs have shown teratogenic effects in animals, there is no data clearly demonstrating these effects in humans.

Studies have shown few, if any, problems with albuterol. However, a couple of very small studies demonstrated found an increased risk of gastroschisis, a birth defect in which an infant is born with some or all of their intestines on the outside of the abdomen due to an abnormal opening in the abdominal muscle wall.

One problem with some of the outcome studies demonstrating potential harm is that SABA use is associated with poorly controlled asthma, which can lead to many of the previously described complications.

SABAs are sometimes used to prevent premature labor. Rather than inhaled, these drugs are given through an IV. The most common side effect seen with this route of administration is hyperglycemia (elevated blood sugar). When infants are born, they sometimes have elevated heart rates, tremors, and low blood sugar as a result of maternal SABA treatment. All of these side effects in the newborn are treatable and usually reverse fairly quickly.

LABAs

Experience with long-acting beta-agonists (LABAs) in pregnancy is much less significant than with SABAs. Based on currently available experience, which includes both human and animal studies, it does not seem that salmeterol or formoterol increases the risk of congenital anomalies. There is more direct human experience with salmeterol.

As a result, it is reasonable in pregnancy to continue a LABA that was needed for asthma control in the pre-pregnant state. The risk of congenital malformations with a lower-dose combination of LABA and inhaled steroids appears to be similar to a medium- or high-dose steroid alone.

Epinephrine

Because of the risk of decreased blood flow to the placenta, the Working Group on Pregnancy and Asthma recommends that epinephrine only be used in the setting of anaphylaxis.

Oral Steroids

Oral steroids are commonly used in pregnancy for a variety of conditions other than asthma. Some of the concerns regarding their use include:

  • Increased risk of prematurity
  • Congenital malformations (mostly cleft palate)
  • Pregnancy-induced hypertension
  • Gestational diabetes
  • Low birth weight
  • Neonatal adrenal insufficiency

There are few definitive answers about how substantial these risks are. For example, some studies have shown an increased risk of cleft palate, and others have not. The evidence demonstrating premature birth among women receiving steroids throughout pregnancy is a little stronger. Finally, hypertension and elevated glucose levels are known complications and therefore not surprising.

So it really comes down to weighing risks. There is a significant risk to mother and fetus related to poor asthma control. The risks of severely uncontrolled asthma would seem to outweigh the potential risks of steroids for most patients.

Inhaled Steroids

The safety data for inhaled steroids during pregnancy, like that for non-pregnant patients, is much more reassuring.

A registry study of the inhaled steroid budesonide in Swedish women showed no increased risk of malformations compared to the general population. The study also showed no complications related to fetal growth, mortality, or prematurity.

In another database-like study, fluticasone showed no increases in congenital malformations compared to other inhaled steroids. Two randomized controlled trials demonstrated improved lung function and decreased rates of readmission.

Leukotriene Modifiers

Like LABAs, this class of drug has only a small clinical experience to date, but the data with Singulair (montelukast) is growing. Unpublished data from the Merck Pregnancy Registry and a prospective, controlled trial indicate that rates of congenital malformations do not appear to be different from the general population.

As a result, patients needing a leukotriene modifier would be better served by montelukast until more data is available from other agents.

Anti-immunoglobulin E

Monoclonal anti-immunoglobulin E antibody or Xolair (omalizumab) is approved for patients with poorly controlled asthma with elevated levels of IgE despite the use of inhaled steroids.

While not formally evaluated in clinical studies, the rates of complications such as miscarriage, preterm birth, small-for-gestational-age infants, and congenital anomalies appear to be similar to other studies.

There is not currently enough data to make a recommendation for its use in pregnancy.

Methylxanthines

There is extensive clinical experience with theophylline and aminophylline in pregnancy. While these drugs are clinically safe, their metabolism is changed significantly in pregnancy and levels must be monitored. The therapeutic range is very small, which makes treatment in non-pregnant patients difficult.

Further, just as in non-pregnant patients, inhaled steroids are more effective for asthma control. As a result, these drugs are best thought of as add-on agents if control can't be achieved with inhaled steroids.

Immunotherapy

While it is not recommended that people start immunotherapy during pregnancy, it does not appear these treatments create additional risk to the mother or fetus, so they can be continued during pregnancy.

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