Halting Asthma Medication For Pregnancy Tied To Adverse Perinatal Outcomes

Pregnant women who discontinue prescribed asthma medicines may be more likely to have infants that are very premature or small for gestational age, a new study suggests.

Researchers examined data on all births after 24 weeks gestation from 2000 to 2010 in Wales that had linked records on maternal prescriptions. The analysis included records on 107,573 women, including 12,690 who were prescribed at least one type of asthma medication before or during pregnancy; a total of 3,589 of these women (28.3%) received their last prescription prior to pregnancy and were considered to have discontinued treatment.

Any asthma medication prescription, whether continued or discontinued during pregnancy, was associated with an increased risk of birth before 32 weeks gestation (adjusted odds ratio 1.33), small for gestational age infants below the 10th centile (aOR 1.10), and lower odds of breastfeeding (aOR 0.93).

Every type of asthma medication was associated with small for gestational age infants below the 10th centile except for monotherapy with inhaled corticosteroids or inhaled short-acting beta-2 agonists.

When women discontinued asthma medications, however, they had an increased risk of births before 37 weeks gestation (aOR 1.22) and before 32 weeks gestation (aOR 1.53), according to the results published in PLoS ONE.

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"We think this may have been because their asthma was no longer under control," said study co-author Sue Jordan of the Faculty of Health and Life Sciences at Swansea University in the UK.

"It is possible that return of even mild asthma may reduce lung function and oxygen availability, which, in turn, can trigger preterm birth," Jordan said by email. "Discontinuing asthma medicines during pregnancy appears to be more harmful than continuing."

Compared to women without asthma, women with asthma were overall more likely to have premature birth before 37 weeks (aOR 1.08) and before 32 weeks (aOR 1.33) as well as babies small for gestational age below the 10th centile (aOR 1.10).

The risk of premature birth before 37 weeks and before 32 weeks was greater with unmedicated asthma than with medicated asthma (aOR 1.22 and 1.53, respectively).

The majority of women prescribed asthma medicines during pregnancy (92.4%) took short-acting beta-2 agonists, and 45.4% of women with these prescriptions took no other asthma medicines.

One limitation of the study is that researchers lacked data on the circumstances surrounding preterm births as well as information on spirometry, oxygen saturation, or psychosocial stressors.

However, the association between asthma and complications such as preterm delivery and small for gestational age is well-established, particularly for women with severe asthma, said Dr. Eyal Sheiner of Ben-Gurion University of the Negev in Beer-Sheva, Israel.

Ideally, women with asthma should try to conceive when the disease is well controlled, Dr. Sheiner, who wasn't involved in the study, said by email.

"The associations between un-medicated asthma and premature birth support the consensus that uncontrolled asthma increases the risk of adverse perinatal outcomes subsequent to premature birth," Dr. Sheiner said. "Discontinuation of prescriptions for asthma in pregnancy offer primary care practitioners a convenient marker to identify pregnancies at increased risk for intervention."

—Lisa Rapaport

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