Research looking at the use of asthma medications during early pregnancy and the risk of specific major birth defects has been published early online in Pediatrics. 

The authors note that asthma affects 4-12% of pregnant women.  Current guidelines recommend that these women continue their asthma medication during pregnancy, and approximately 3% of pregnant women report using asthma medications.  Safety data regarding the use of many asthma medications during pregnancy are however sparse and few studies have examined major birth defects as primary outcomes; many have been limited due to small numbers of cases for specific birth defects. 

In their study, they used data from the ongoing population-based National Birth Defects Prevention Study (NBDPS) in the US to examine whether maternal use of asthma medication during early pregnancy increased the risk of selected birth defects, after controlling for potential confounders.  They identified 2,853 cases, that is live births, stillbirths, or elective terminations diagnosed with one of the following: neural tube defects (further divided into 2 groups: anencephaly and spina bifida), oesophageal atresia, small intestinal atresia, anorectal atresia, limb deficiencies, diaphragmatic hernia, and omphalocele (these were selected as there were over 200 cases for each).  Cases were matched to 6,726 unaffected control infants.  Mothers of the cases and controls were questioned about medication use and the presence of other potential risk factors.

Exposure was defined as reported use of asthma medication at least once during the peri-conceptional period; those reporting use ‘as needed’ with an unknown time period of use were excluded from the analysis to reduce misclassification.  Potential confounders examined included infant gender, maternal age, BMI, parity, race/ethnicity, education, alcohol use, smoking, folic acid–containing vitamin use, fever, and crack/cocaine use.  Salbutamol was the most frequently reported bronchodilator (2.75% cases and 2.11% controls) and fluticasone (1.22% cases and 0.77% controls) was the most frequently reported anti-inflammatory used. All other medications were reportedly used by a very small proportion (<0.5%) of cases or controls.

The authors report that positive associations between maternal asthma medication use and specific defects were found for isolated oesophageal atresia (bronchodilator use: adjusted odds ratio [aOR] 2.39, 95% CI 1.23-4.66), isolated anorectal atresia (anti-inflammatory use: aOR 2.12, 95% CI 1.09-4.12) and omphalocele (bronchodilator and anti-inflammatory use: aOR 4.13, 95% CI 1.43-11.95).  No statistically significant associations were found for maternal astma medication use and the other defects studied.  

The authors comment that the observed observations could be due to chance, or could be related to asthma severity and related hypoxia, rather than use of medications.  They therefore recommend that no changes be made to the current clinical guidelines on the management of asthma during pregnancy, but call for additional large studies on this topic collecting detailed data on asthma severity and treatment, to help clarify the associations, if any.