Get Help

Call the Lung Health Line


Our certified respiratory
educators are ready to take your questions
(M-F 8:30am-4:30pm)

Asthma and pregnancy

PREGNANT WOMEN ARE BREATHING FOR TWO. When asthma is controlled, women with asthma have no more complications during pregnancy and giving birth than women who don’t have asthma. However, uncontrolled asthma during pregnancy can lead to serious maternal and fetal complications. If you have asthma and you’re pregnant or planning to become pregnant, see your doctor.

When you’re pregnant, it’s especially important to have your asthma under good control. Breathing difficulties in the mother can limit the oxygen supply to the fetus. Take the Asthma Control Check to ensure your asthma is under control.

How asthma changes when you’re pregnant

In general, one third of pregnant women with asthma notice that their asthma symptoms improve during pregnancy; one third of women have asthma symptoms that stay the same, and one third of women have asthma symptoms that get worse.


If a mother has uncontrolled asthma, there is a higher risk for:

  • Premature birth
  • Low birth weight
  • Maternal blood pressure changes (i.e., pre-eclampsia)

Controlling asthma while you’re pregnant

Acute asthma episodes endanger the fetus by reducing the oxygen it receives. It is therefore important to prevent asthma episodes during pregnancy and labour and delivery. Some ways to prevent asthma episodes:

  • Control your environment: avoid your asthma triggers. Avoiding triggers should be the first form of asthma therapy during pregnancy.
  • Continue taking your regular asthma medications (as prescribed by your doctor) during pregnancy and labour and delivery.
  • Ask your doctor about getting a flu shot. This shot is recommended for almost everyone, and especially people with asthma.
  • Don’t smoke. A pregnant woman who smokes runs a greatly increased risk of having a severe asthma episode at some time in the pregnancy. This could seriously reduce the oxygen supply to the fetus.
  • Avoid second hand smoke. Both you and your baby can be hurt by second-hand smoke. Ask friends and family not to smoke near you or in your home or car.

Asthma medications and pregnancy

Most asthma medications are safe during pregnancy. Generally, the risks of uncontrolled asthma are far greater than the risks to the mother or fetus from most of the medications used to control asthma. If you are pregnant or plan to become pregnant, tell your doctor. Your doctor may change your medications, depending on what you are taking.

Asthma care should be integrated with obstetric care. The same health care provider if possible should be used for both. A team approach should be used if more than one doctor is involved.

Medications to avoid

There are many over-the counter, prescription and herbal medications that should not be taken during pregnancy. Check with your doctor or pharmacist before you take any over-the-counter, prescription or herbal medicine if you are pregnant.

You can also learn more about healthy pregnancy and medications from Motherisk, a free, evidence-based pregnancy and drug information service based at the Hospital for Sick Children in Toronto.

Medications during labour and delivery

The mother’s regularly scheduled asthma medications should be continued during labour and delivery. For the women whose asthma improved during pregnancy, and their medications appropriately reduced, an increased need for medication may occur immediately following delivery.

If your asthma has not been under good control, your doctor may give you specific instructions to go to the hospital earlier in the labour.

Monitoring asthma during pregnancy

Your doctor may want you to do a lung function test to see how your breathing is doing. By assessing and monitoring your lung function, your doctor can make any needed medication changes. The doctor can monitor your asthma by using:

  • Spirometry: a simple breathing test that measures how much air you can push out of your lungs, and how fast
  • A peak flow meter: a hand held device that measures how fast you can blow air out of your lungs

The goal is to try and maintain normal, or near normal lung function.

Monitoring during labour and delivery

The mother and fetus are monitored during labour and delivery to ensure the good health of both. This is especially necessary for women with asthma.

Fetus: As in most labours, the fetus is monitored electronically on admission to hospital. If the mother’s asthma is under control and in low-risk patients, continuous monitoring may not be necessary. During the course of labour, continuous fetal monitoring may be considered.

Mother: You will have a peak flow rate taken on admission to labour and delivery unit, and every 12 hours following. If asthma symptoms develop, peak flow rates should be measured after treatments.

Asthma after the baby is born (post-natal period)

  • After the baby is born, it may be necessary to change your asthma medications and doses. Because some women experience changes in their asthma during pregnancy, the asthma may again change following delivery.
  • The postpartum period can involve anxiety surrounding the newborn, fatigue, and possibly significant postpartum depression. For this reason, you and your doctor should monitor your asthma very closely to make sure it stays well-controlled.
  • Avoid smoke. Infants are twice as likely to die of sudden infant death syndrome (SIDS) if their mother starts smoking again after giving birth. To keep your baby healthy, don’t smoke and don’t let anyone smoke around your child or in your home or vehicle. Children of parents who smoke have a much higher rate of colds and other upper respiratory infections compared to children whose parents do not smoke.


  • Inhaled bronchodilators and inhaled anti-inflammatories do not appear to cause side effects.
  • Theophylline gets into breast milk and can make the baby irritable.
  • Antihistimines should be avoided because they can cause sleeplessness and irritability in children. They can also reduce or prevent production of breast milk.